Psql documentation notes for windows users

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psql (1)

NAME

psql - PostgreSQL interactive terminal

SYNOPSIS

psql [ option… ] [ dbname

 [ username ]  ] 
 

DESCRIPTION

psql is a terminal-based front-end to
PostgreSQL. It enables you to type in
queries interactively, issue them to
PostgreSQL, and see the query results.
Alternatively, input can be from a file. In addition, it provides a
number of meta-commands and various shell-like features to
facilitate writing scripts and automating a wide variety of tasks.
 

OPTIONS

-a

—echo-all

Print all input lines to standard output as they are read. This is more
useful for script processing rather than interactive mode. This is
equivalent to setting the variable ECHO to
all.

-A

—no-align

Switches to unaligned output mode. (The default output mode is
otherwise aligned.)

-c command

—command command

Specifies that psql is to execute one
command string, command,
and then exit. This is useful in shell scripts.

command must be either
a command string that is completely parsable by the server (i.e.,
it contains no psql specific features),
or a single backslash command. Thus you cannot mix
SQL and psql
meta-commands. To achieve that, you could pipe the string into
psql, like this: echo «\x \\
select * from foo;» | psql.

If the command string contains multiple SQL commands, they are
processed in a single transaction, unless there are explicit
BEGIN/COMMIT commands included in the string to divide it into
multiple transactions. This is different from the behavior when
the same string is fed to psql‘s standard input.

-d dbname

—dbname dbname

Specifies the name of the database to connect to. This is
equivalent to specifying dbname as the first non-option
argument on the command line.

-e

—echo-queries

Copy all SQL commands sent to the server to standard output as well.
This is equivalent
to setting the variable ECHO to
queries.

-E

—echo-hidden

Echo the actual queries generated by \d and other backslash
commands. You can use this to study psql‘s
internal operations. This is equivalent to
setting the variable ECHO_HIDDEN from within
psql.

-f filename

—file filename

Use the file filename
as the source of commands instead of reading commands interactively.
After the file is processed, psql
terminates. This is in many ways equivalent to the internal
command \i.

If filename is —
(hyphen), then standard input is read.

Using this option is subtly different from writing psql
< filename. In general,
both will do what you expect, but using -f
enables some nice features such as error messages with line
numbers. There is also a slight chance that using this option will
reduce the start-up overhead. On the other hand, the variant using
the shell’s input redirection is (in theory) guaranteed to yield
exactly the same output that you would have gotten had you entered
everything by hand.

-F separator

—field-separator separator

Use separator as the
field separator for unaligned output. This is equivalent to
\pset fieldsep or \f.

-h hostname

—host hostname

Specifies the host name of the machine on which the
server is running. If the value begins
with a slash, it is used as the directory for the Unix-domain
socket.

-H

—html

Turn on HTML tabular output. This is
equivalent to \pset format html or the
\H command.

-l

—list

List all available databases, then exit. Other non-connection
options are ignored. This is similar to the internal command
\list.

-L filename

—log-file filename

Write all query output into file filename, in addition to the
normal output destination.

-o filename

—output filename

Put all query output into file filename. This is equivalent to
the command \o.

-p port

—port port

Specifies the TCP port or the local Unix-domain
socket file extension on which the server is listening for
connections. Defaults to the value of the PGPORT
environment variable or, if not set, to the port specified at
compile time, usually 5432.

-P assignment

—pset assignment

Allows you to specify printing options in the style of
\pset on the command line. Note that here you
have to separate name and value with an equal sign instead of a
space. Thus to set the output format to LaTeX, you could write
-P format=latex.

-q

—quiet

Specifies that psql should do its work
quietly. By default, it prints welcome messages and various
informational output. If this option is used, none of this
happens. This is useful with the -c option.
Within psql you can also set the
QUIET variable to achieve the same effect.

-R separator

—record-separator separator

Use separator as the
record separator for unaligned output. This is equivalent to the
\pset recordsep command.

-s

—single-step

Run in single-step mode. That means the user is prompted before
each command is sent to the server, with the option to cancel
execution as well. Use this to debug scripts.

-S

—single-line

Runs in single-line mode where a newline terminates an SQL command, as a
semicolon does.

Note:

This mode is provided for those who insist on it, but you are not
necessarily encouraged to use it. In particular, if you mix
SQL and meta-commands on a line the order of
execution might not always be clear to the inexperienced user.

-t

—tuples-only

Turn off printing of column names and result row count footers,
etc. This is equivalent to the \t command.

-T table_options

—table-attr table_options

Allows you to specify options to be placed within the
HTML table tag. See
\pset for details.

-u

Forces psql to prompt for the user name and
password before connecting to the database.

This option is deprecated, as it is conceptually flawed.
(Prompting for a non-default user name and prompting for a
password because the server requires it are really two different
things.) You are encouraged to look at the -U and
-W options instead.

-U username

—username username

Connect to the database as the user username instead of the default.
(You must have permission to do so, of course.)

-v assignment

—set assignment

—variable assignment

Perform a variable assignment, like the \set
internal command. Note that you must separate name and value, if
any, by an equal sign on the command line. To unset a variable,
leave off the equal sign. To just set a variable without a value,
use the equal sign but leave off the value. These assignments are
done during a very early stage of start-up, so variables reserved
for internal purposes might get overwritten later.

-V

—version

Print the psql version and exit.

-W

—password

Forces psql to prompt for a
password before connecting to a database.

psql should automatically prompt for a
password whenever the server requests password authentication.
However, currently password request detection is not totally
reliable, hence this option to force a prompt. If no password
prompt is issued and the server requires password authentication,
the connection attempt will fail.

This option will remain set for the entire session, even if you
change the database connection with the meta-command
\connect.

-x

—expanded

Turn on the expanded table formatting mode. This is equivalent to the
\x command.

-X,

—no-psqlrc

Do not read the start-up file (neither the system-wide
psqlrc file nor the user’s
~/.psqlrc file).

-?

—help

Show help about psql command line
arguments, and exit.

EXIT STATUS

psql returns 0 to the shell if it
finished normally, 1 if a fatal error of its own (out of memory,
file not found) occurs, 2 if the connection to the server went bad
and the session was not interactive, and 3 if an error occurred in a
script and the variable ON_ERROR_STOP was set.
 

USAGE

CONNECTING TO A DATABASE

psql is a regular
PostgreSQL client application. In order
to connect to a database you need to know the name of your target
database, the host name and port number of the server and what user
name you want to connect as. psql can be
told about those parameters via command line options, namely
-d, -h, -p, and
-U respectively. If an argument is found that does
not belong to any option it will be interpreted as the database name
(or the user name, if the database name is already given). Not all
these options are required; there are useful defaults. If you omit the host
name, psql will connect via a Unix-domain socket
to a server on the local host, or via TCP/IP to localhost on
machines that don’t have Unix-domain sockets. The default port number is
determined at compile time.
Since the database server uses the same default, you will not have
to specify the port in most cases. The default user name is your
Unix user name, as is the default database name. Note that you can’t
just connect to any database under any user name. Your database
administrator should have informed you about your access rights.

When the defaults aren’t quite right, you can save yourself
some typing by setting the environment variables
PGDATABASE, PGHOST,
PGPORT and/or PGUSER to appropriate
values. (For additional environment variables, see the documentation.) It is also convenient to have a
~/.pgpass file to avoid regularly having to type in
passwords. See the documentation for more information.

If the connection could not be made for any reason (e.g., insufficient
privileges, server is not running on the targeted host, etc.),
psql will return an error and terminate.
 

ENTERING SQL COMMANDS

In normal operation, psql provides a
prompt with the name of the database to which
psql is currently connected, followed by
the string =>. For example,

$ psql testdb
Welcome to psql 8.1.11, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help with psql commands
       \g or terminate with semicolon to execute query
       \q to quit

testdb=>

At the prompt, the user may type in SQL commands.
Ordinarily, input lines are sent to the server when a
command-terminating semicolon is reached. An end of line does not
terminate a command. Thus commands can be spread over several lines for
clarity. If the command was sent and executed without error, the results
of the command are displayed on the screen.

Whenever a command is executed, psql also polls
for asynchronous notification events generated by
LISTEN [listen(7)] and
NOTIFY [notify(7)].
 

META-COMMANDS

Anything you enter in psql that begins
with an unquoted backslash is a psql
meta-command that is processed by psql
itself. These commands help make
psql more useful for administration or
scripting. Meta-commands are more commonly called slash or backslash
commands.

The format of a psql command is the backslash,
followed immediately by a command verb, then any arguments. The arguments
are separated from the command verb and each other by any number of
whitespace characters.

To include whitespace into an argument you may quote it with a
single quote. To include a single quote into such an argument,
precede it by a backslash. Anything contained in single quotes is
furthermore subject to C-like substitutions for
\n (new line), \t (tab),
\digits (octal), and
\xdigits (hexadecimal).

If an unquoted argument begins with a colon (:),
it is taken as a psql variable and the value of the
variable is used as the argument instead.

Arguments that are enclosed in backquotes (`)
are taken as a command line that is passed to the shell. The
output of the command (with any trailing newline removed) is taken
as the argument value. The above escape sequences also apply in
backquotes.

Some commands take an SQL identifier (such as a
table name) as argument. These arguments follow the syntax rules
of SQL: Unquoted letters are forced to
lowercase, while double quotes («) protect letters
from case conversion and allow incorporation of whitespace into
the identifier. Within double quotes, paired double quotes reduce
to a single double quote in the resulting name. For example,
FOO»BAR»BAZ is interpreted as fooBARbaz,
and «A weird»» name» becomes A weird»
name.

Parsing for arguments stops when another unquoted backslash occurs.
This is taken as the beginning of a new meta-command. The special
sequence \\ (two backslashes) marks the end of
arguments and continues parsing SQL commands, if
any. That way SQL and
psql commands can be freely mixed on a
line. But in any case, the arguments of a meta-command cannot
continue beyond the end of the line.

The following meta-commands are defined:

\a

If the current table output format is unaligned, it is switched to aligned.
If it is not unaligned, it is set to unaligned. This command is
kept for backwards compatibility. See \pset for a
more general solution.

\cd [ directory ]

Changes the current working directory to
directory. Without argument, changes
to the current user’s home directory.

Tip:

To print your current working directory, use \!pwd.

\C [ title ]

Sets the title of any tables being printed as the result of a
query or unset any such title. This command is equivalent to
\pset title title. (The name of
this command derives from «caption», as it was
previously only used to set the caption in an
HTML table.)

\connect (or \c) [ dbname [ username ] ]

Establishes a connection to a new database and/or under a user
name. The previous connection is closed. If dbname is —
the current database name is assumed.

If username is
omitted the current user name is assumed.

As a special rule, \connect without any
arguments will connect to the default database as the default
user (as you would have gotten by starting
psql without any arguments).

If the connection attempt failed (wrong user name, access
denied, etc.), the previous connection will be kept if and only
if psql is in interactive mode. When
executing a non-interactive script, processing will immediately
stop with an error. This distinction was chosen as a user
convenience against typos on the one hand, and a safety
mechanism that scripts are not accidentally acting on the wrong
database on the other hand.

\copy table

Performs a frontend (client) copy. This is an operation that
runs an SQL COPY [copy(7)] command, but instead of the server
reading or writing the specified file,
psql reads or writes the file and
routes the data between the server and the local file system.
This means that file accessibility and privileges are those of
the local user, not the server, and no SQL superuser
privileges are required.

The syntax of the command is similar to that of the
SQL COPY [copy(7)] command. Note that, because of this,
special parsing rules apply to the \copy
command. In particular, the variable substitution rules and
backslash escapes do not apply.

\copy table from stdin | stdout
reads/writes based on the command input and output respectively.
All rows are read from the same source that issued the command,
continuing until \. is read or the stream
reaches EOF. Output is sent to the same place as
command output. To read/write from
psql‘s standard input or output, use
pstdin or pstdout. This option is useful
for populating tables in-line within a SQL script file.

Tip:

This operation is not as efficient as the SQL
COPY command because all data must pass
through the client/server connection. For large
amounts of data the SQL command may be preferable.

\copyright

Shows the copyright and distribution terms of
PostgreSQL.

\d [ pattern ]

\d+ [ pattern ]

For each relation (table, view, index, or sequence) matching the
pattern, show all
columns, their types, the tablespace (if not the default) and any special
attributes such as NOT NULL or defaults, if
any. Associated indexes, constraints, rules, and triggers are
also shown, as is the view definition if the relation is a view.
(«Matching the pattern» is defined below.)

The command form \d+ is identical, except that
more information is displayed: any comments associated with the
columns of the table are shown, as is the presence of OIDs in the
table.

Note:

If \d is used without a
pattern argument, it is
equivalent to \dtvs which will show a list of
all tables, views, and sequences. This is purely a convenience
measure.

\da [ pattern ]

Lists all available aggregate functions, together with the data
type they operate on. If pattern
is specified, only aggregates whose names match the pattern are shown.

\db [ pattern ]

\db+ [ pattern ]

Lists all available tablespaces. If pattern
is specified, only tablespaces whose names match the pattern are shown.
If + is appended to the command name, each object
is listed with its associated permissions.

\dc [ pattern ]

Lists all available conversions between character-set encodings.
If pattern
is specified, only conversions whose names match the pattern are
listed.

\dC

Lists all available type casts.

\dd [ pattern ]

Shows the descriptions of objects matching the pattern, or of all visible objects if
no argument is given. But in either case, only objects that have
a description are listed.
(«Object» covers aggregates, functions, operators,
types, relations (tables, views, indexes, sequences, large
objects), rules, and triggers.) For example:

=> \dd version
                     Object descriptions
   Schema   |  Name   |  Object  |        Description
------------+---------+----------+---------------------------
 pg_catalog | version | function | PostgreSQL version string
(1 row)

Descriptions for objects can be created with the COMMENT [comment(7)]
SQL command.

\dD [ pattern ]

Lists all available domains. If pattern
is specified, only matching domains are shown.

\df [ pattern ]

\df+ [ pattern ]

Lists available functions, together with their argument and
return types. If pattern
is specified, only functions whose names match the pattern are shown.
If the form \df+ is used, additional information about
each function, including language and description, is shown.

Note:

To look up functions taking argument or returning values of a specific
type, use your pager’s search capability to scroll through the \df
output.

To reduce clutter, \df does not show data type I/O
functions. This is implemented by ignoring functions that accept
or return type cstring.

\dg [ pattern ]

Lists all database roles. If pattern is specified, only
those roles whose names match the pattern are listed.
(This command is now effectively the same as \du.)

\distvS [ pattern ]

This is not the actual command name: the letters
i, s, t,
v, S stand for index,
sequence, table, view, and system table, respectively. You can
specify any or all of these letters, in any order, to obtain a
listing of all the matching objects. The letter S restricts the
listing to system objects; without S, only
non-system objects are shown. If + is appended
to the command name, each object is listed with its associated
description, if any.

If pattern is
specified, only objects whose names match the pattern are listed.

\dl

This is an alias for \lo_list, which shows a
list of large objects.

\dn [ pattern ]

\dn+ [ pattern ]

Lists all available schemas (namespaces). If pattern (a regular expression)
is specified, only schemas whose names match the pattern are listed.
Non-local temporary schemas are suppressed. If +
is appended to the command name, each object is listed with its associated
permissions and description, if any.

\do [ pattern ]

Lists available operators with their operand and return types.
If pattern is
specified, only operators whose names match the pattern are listed.

\dp [ pattern ]

Produces a list of all available tables, views and sequences with their
associated access privileges.
If pattern is
specified, only tables, views and sequences whose names match the pattern are listed.

The commands GRANT and
REVOKE are used to set access privileges.
See GRANT [grant(7)]
for more information.

\dT [ pattern ]

\dT+ [ pattern ]

Lists all data types or only those that match pattern. The command form
\dT+ shows extra information.

\du [ pattern ]

Lists all database roles, or only those that match pattern.

\edit (or \e) [ filename ]

If filename is
specified, the file is edited; after the editor exits, its
content is copied back to the query buffer. If no argument is
given, the current query buffer is copied to a temporary file
which is then edited in the same fashion.

The new query buffer is then re-parsed according to the normal
rules of psql, where the whole buffer
is treated as a single line. (Thus you cannot make scripts this
way. Use \i for that.) This means also that
if the query ends with (or rather contains) a semicolon, it is
immediately executed. In other cases it will merely wait in the
query buffer.

Tip:

psql searches the environment
variables PSQL_EDITOR, EDITOR, and
VISUAL (in that order) for an editor to use. If
all of them are unset, vi is used on Unix
systems, notepad.exe on Windows systems.

\echo text [ … ]

Prints the arguments to the standard output, separated by one
space and followed by a newline. This can be useful to
intersperse information in the output of scripts. For example:

=> \echo `date`
Tue Oct 26 21:40:57 CEST 1999

If the first argument is an unquoted -n the trailing
newline is not written.

Tip:

If you use the \o command to redirect your
query output you may wish to use \qecho
instead of this command.

\encoding [ encoding ]

Sets the client character set encoding. Without an argument, this command
shows the current encoding.

\f [ string ]

Sets the field separator for unaligned query output. The default
is the vertical bar (|). See also
\pset for a generic way of setting output
options.

\g [ { filename | |command } ]

Sends the current query input buffer to the server and
optionally stores the query’s output in filename or pipes the output
into a separate Unix shell executing command. A bare
\g is virtually equivalent to a semicolon. A
\g with argument is a «one-shot»
alternative to the \o command.

\help (or \h) [ command ]

Gives syntax help on the specified SQL
command. If command
is not specified, then psql will list
all the commands for which syntax help is available. If
command is an
asterisk (*), then syntax help on all
SQL commands is shown.

Note:

To simplify typing, commands that consists of several words do
not have to be quoted. Thus it is fine to type \help
alter table.

\H

Turns on HTML query output format. If the
HTML format is already on, it is switched
back to the default aligned text format. This command is for
compatibility and convenience, but see \pset
about setting other output options.

\i filename

Reads input from the file filename and executes it as
though it had been typed on the keyboard.

Note:

If you want to see the lines on the screen as they are read you
must set the variable ECHO to
all.

\l (or \list)

\l+ (or \list+)

List the names, owners, and character set encodings of all the databases in
the server. If + is appended to the command
name, database descriptions are also displayed.

\lo_export loid filename

Reads the large object with OID loid from the database and
writes it to filename. Note that this is
subtly different from the server function
lo_export, which acts with the permissions
of the user that the database server runs as and on the server’s
file system.

Tip:

Use \lo_list to find out the large object’s
OID.

\lo_import filename [ comment ]

Stores the file into a PostgreSQL
large object. Optionally, it associates the given
comment with the object. Example:

foo=> \lo_import '/home/peter/pictures/photo.xcf' 'a picture of me'
lo_import 152801

The response indicates that the large object received object ID
152801 which one ought to remember if one wants to access the
object ever again. For that reason it is recommended to always
associate a human-readable comment with every object. Those can
then be seen with the \lo_list command.

Note that this command is subtly different from the server-side
lo_import because it acts as the local user
on the local file system, rather than the server’s user and file
system.

\lo_list

Shows a list of all PostgreSQL
large objects currently stored in the database,
along with any comments provided for them.

\lo_unlink loid

Deletes the large object with OID
loid from the
database.

Tip:

Use \lo_list to find out the large object’s
OID.

\o [ {filename | |command} ]

Saves future query results to the file filename or pipes future results
into a separate Unix shell to execute command. If no arguments are
specified, the query output will be reset to the standard output.

«Query results» includes all tables, command
responses, and notices obtained from the database server, as
well as output of various backslash commands that query the
database (such as \d), but not error
messages.

Tip:

To intersperse text output in between query results, use
\qecho.

\p

Print the current query buffer to the standard output.

\pset parameter [ value ]

This command sets options affecting the output of query result
tables. parameter
describes which option is to be set. The semantics of
value depend
thereon.

Adjustable printing options are:

format

Sets the output format to one of unaligned,
aligned, html,
latex, or troff-ms.
Unique abbreviations are allowed. (That would mean one letter
is enough.)

«Unaligned» writes all columns of a row on a
line, separated by the currently active field separator. This
is intended to create output that might be intended to be read
in by other programs (tab-separated, comma-separated).
«Aligned» mode is the standard, human-readable,
nicely formatted text output that is default. The
«HTML» and
«LaTeX» modes put out tables that are intended to
be included in documents using the respective mark-up
language. They are not complete documents! (This might not be
so dramatic in HTML, but in LaTeX you must
have a complete document wrapper.)

border

The second argument must be a number. In general, the higher
the number the more borders and lines the tables will have,
but this depends on the particular format. In
HTML mode, this will translate directly
into the border=… attribute, in the
others only values 0 (no border), 1 (internal dividing lines),
and 2 (table frame) make sense.

expanded (or x)

Toggles between regular and expanded format. When expanded
format is enabled, query results are displayed in two
columns, with the column name on the left and the data on
the right. This mode is useful if the data wouldn’t fit on the
screen in the normal «horizontal» mode.

Expanded mode is supported by all four output formats.

null

The second argument is a string that should be printed
whenever a column is null. The default is not to print
anything, which can easily be mistaken for, say, an empty
string. Thus, one might choose to write \pset null
‘(null)’.

fieldsep

Specifies the field separator to be used in unaligned output
mode. That way one can create, for example, tab- or
comma-separated output, which other programs might prefer. To
set a tab as field separator, type \pset fieldsep
‘\t’. The default field separator is
‘|’ (a vertical bar).

footer

Toggles the display of the default footer (x
rows).

numericlocale

Toggles the display of a locale-aware character to separate groups
of digits to the left of the decimal marker. It also enables
a locale-aware decimal marker.

recordsep

Specifies the record (line) separator to use in unaligned
output mode. The default is a newline character.

tuples_only (or t)

Toggles between tuples only and full display. Full display may
show extra information such as column headers, titles, and
various footers. In tuples only mode, only actual table data
is shown.

title [ text ]

Sets the table title for any subsequently printed tables. This
can be used to give your output descriptive tags. If no
argument is given, the title is unset.

tableattr (or T) [ text ]

Allows you to specify any attributes to be placed inside the
HTML table tag. This
could for example be cellpadding or
bgcolor. Note that you probably don’t want
to specify border here, as that is already
taken care of by \pset border.

pager

Controls use of a pager for query and psql
help output. If the environment variable PAGER
is set, the output is piped to the specified program.
Otherwise a platform-dependent default (such as
more) is used.

When the pager is off, the pager is not used. When the pager
is on, the pager is used only when appropriate, i.e. the
output is to a terminal and will not fit on the screen.
(psql does not do a perfect job of estimating
when to use the pager.) \pset pager turns the
pager on and off. Pager can also be set to always,
which causes the pager to be always used.

Illustrations on how these different formats look can be seen in
the Examples [psql(1)] section.

Tip:

There are various shortcut commands for \pset. See
\a, \C, \H,
\t, \T, and \x.

Note:

It is an error to call \pset without
arguments. In the future this call might show the current status
of all printing options.

\q

Quits the psql program.

\qecho text [ … ]

This command is identical to \echo except
that the output will be written to the query output channel, as
set by \o.

\r

Resets (clears) the query buffer.

\s [ filename ]

Print or save the command line history to filename. If filename is omitted, the history
is written to the standard output. This option is only available
if psql is configured to use the
GNU Readline library.

\set [ name [ value [ … ] ] ]

Sets the internal variable name to value or, if more than one value
is given, to the concatenation of all of them. If no second
argument is given, the variable is just set with no value. To
unset a variable, use the \unset command.

Valid variable names can contain characters, digits, and
underscores. See the section Variables [psql(1)] below for details.
Variable names are case-sensitive.

Although you are welcome to set any variable to anything you
want, psql treats several variables
as special. They are documented in the section about variables.

Note:

This command is totally separate from the SQL
command SET [set(7)].

\t

Toggles the display of output column name headings and row count
footer. This command is equivalent to \pset
tuples_only and is provided for convenience.

\T table_options

Allows you to specify attributes to be placed within the
table tag in HTML tabular
output mode. This command is equivalent to \pset
tableattr table_options.

\timing

Toggles a display of how long each SQL statement takes, in milliseconds.

\w {filename | |command}

Outputs the current query buffer to the file filename or pipes it to the Unix
command command.

\x

Toggles expanded table formatting mode. As such it is equivalent to
\pset expanded.

\z [ pattern ]

Produces a list of all available tables, views and sequences with their
associated access privileges.
If a pattern is
specified, only tables,views and sequences whose names match the pattern are listed.

The commands GRANT and
REVOKE are used to set access privileges.
See GRANT [grant(7)] for
more information.

This is an alias for \dp («display
privileges»).

\! [ command ]

Escapes to a separate Unix shell or executes the Unix command
command. The
arguments are not further interpreted, the shell will see them
as is.

\?

Shows help information about the backslash commands.

The various \d commands accept a pattern parameter to specify the
object name(s) to be displayed. * means «any
sequence of characters» and ? means «any single
character». (This notation is comparable to Unix shell file name
patterns.) Advanced users can also use regular-expression
notations such as character classes, for example [0-9]
to match «any digit». To make any of these
pattern-matching characters be interpreted literally, surround it
with double quotes.

A pattern that contains an (unquoted) dot is interpreted as a schema
name pattern followed by an object name pattern. For example,
\dt foo*.bar* displays all tables in schemas whose name
starts with foo and whose table name
starts with bar. If no dot appears, then the pattern
matches only objects that are visible in the current schema search path.

Whenever the pattern parameter
is omitted completely, the \d commands display all objects
that are visible in the current schema search path. To see all objects
in the database, use the pattern *.*.
 

ADVANCED FEATURES

VARIABLES

psql provides variable substitution
features similar to common Unix command shells.
Variables are simply name/value pairs, where the value
can be any string of any length. To set variables, use the
psql meta-command
\set:

testdb=> \set foo bar

sets the variable foo to the value
bar. To retrieve the content of the variable, precede
the name with a colon and use it as the argument of any slash
command:

testdb=> \echo :foo
bar

Note:

The arguments of \set are subject to the same
substitution rules as with other commands. Thus you can construct
interesting references such as \set :foo
‘something’ and get «soft links» or
«variable variables» of Perl
or PHP fame,
respectively. Unfortunately (or fortunately?), there is no way to do
anything useful with these constructs. On the other hand,
\set bar :foo is a perfectly valid way to copy a
variable.

If you call \set without a second argument, the
variable is set, with an empty string as value. To unset (or delete) a
variable, use the command \unset.

psql‘s internal variable names can
consist of letters, numbers, and underscores in any order and any
number of them. A number of these variables are treated specially
by psql. They indicate certain option
settings that can be changed at run time by altering the value of
the variable or represent some state of the application. Although
you can use these variables for any other purpose, this is not
recommended, as the program behavior might grow really strange
really quickly. By convention, all specially treated variables
consist of all upper-case letters (and possibly numbers and
underscores). To ensure maximum compatibility in the future, avoid
using such variable names for your own purposes. A list of all specially
treated variables follows.

AUTOCOMMIT

When on (the default), each SQL command is automatically
committed upon successful completion. To postpone commit in this
mode, you must enter a BEGIN or START
TRANSACTION SQL command. When off or unset, SQL
commands are not committed until you explicitly issue
COMMIT or END. The autocommit-off
mode works by issuing an implicit BEGIN for you, just
before any command that is not already in a transaction block and
is not itself a BEGIN or other transaction-control
command, nor a command that cannot be executed inside a transaction
block (such as VACUUM).

Note:

In autocommit-off mode, you must explicitly abandon any failed
transaction by entering ABORT or ROLLBACK.
Also keep in mind that if you exit the session
without committing, your work will be lost.

Note:

The autocommit-on mode is PostgreSQL’s traditional
behavior, but autocommit-off is closer to the SQL spec. If you
prefer autocommit-off, you may wish to set it in the system-wide
psqlrc file or your
~/.psqlrc file.

DBNAME

The name of the database you are currently connected to. This is
set every time you connect to a database (including program
start-up), but can be unset.

ECHO

If set to all, all lines
entered from the keyboard or from a script are written to the standard output
before they are parsed or executed. To select this behavior on program
start-up, use the switch -a. If set to
queries,
psql merely prints all queries as
they are sent to the server. The switch for this is
-e.

ECHO_HIDDEN

When this variable is set and a backslash command queries the
database, the query is first shown. This way you can study the
PostgreSQL internals and provide
similar functionality in your own programs. (To select this behavior
on program start-up, use the switch -E.) If you set
the variable to the value noexec, the queries are
just shown but are not actually sent to the server and executed.

ENCODING

The current client character set encoding.

HISTCONTROL

If this variable is set to ignorespace,
lines which begin with a space are not entered into the history
list. If set to a value of ignoredups, lines
matching the previous history line are not entered. A value of
ignoreboth combines the two options. If
unset, or if set to any other value than those above, all lines
read in interactive mode are saved on the history list.

Note:

This feature was shamelessly plagiarized from
Bash.

HISTFILE

The file name that will be used to store the history list. The default
value is ~/.psql_history. For example, putting

\set HISTFILE ~/.psql_history- :DBNAME

in ~/.psqlrc will cause
psql to maintain a separate history for
each database.

Note:

This feature was shamelessly plagiarized from
Bash.

HISTSIZE

The number of commands to store in the command history. The
default value is 500.

Note:

This feature was shamelessly plagiarized from
Bash.

HOST

The database server host you are currently connected to. This is
set every time you connect to a database (including program
start-up), but can be unset.

IGNOREEOF

If unset, sending an EOF character (usually
Control+D)
to an interactive session of psql
will terminate the application. If set to a numeric value,
that many EOF characters are ignored before the
application terminates. If the variable is set but has no
numeric value, the default is 10.

Note:

This feature was shamelessly plagiarized from
Bash.

LASTOID

The value of the last affected OID, as returned from an
INSERT or lo_insert
command. This variable is only guaranteed to be valid until
after the result of the next SQL command has
been displayed.

ON_ERROR_ROLLBACK

When on, if a statement in a transaction block
generates an error, the error is ignored and the transaction
continues. When interactive, such errors are only
ignored in interactive sessions, and not when reading script
files. When off (the default), a statement in a
transaction block that generates an error aborts the entire
transaction. The on_error_rollback-on mode works by issuing an
implicit SAVEPOINT for you, just before each command
that is in a transaction block, and rolls back to the savepoint
on error.

ON_ERROR_STOP

By default, if non-interactive scripts encounter an error, such
as a malformed SQL command or internal
meta-command, processing continues. This has been the
traditional behavior of psql but it
is sometimes not desirable. If this variable is set, script
processing will immediately terminate. If the script was called
from another script it will terminate in the same fashion. If
the outermost script was not called from an interactive
psql session but rather using the
-f option, psql will
return error code 3, to distinguish this case from fatal error
conditions (error code 1).

PORT

The database server port to which you are currently connected.
This is set every time you connect to a database (including
program start-up), but can be unset.

PROMPT1

PROMPT2

PROMPT3

These specify what the prompts psql
issues should look like. See Prompting [psql(1)] below.

QUIET

This variable is equivalent to the command line option
-q. It is probably not too useful in
interactive mode.

SINGLELINE

This variable is equivalent to the command line option
-S.

SINGLESTEP

This variable is equivalent to the command line option
-s.

USER

The database user you are currently connected as. This is set
every time you connect to a database (including program
start-up), but can be unset.

VERBOSITY

This variable can be set to the values default,
verbose, or terse to control the verbosity
of error reports.

SQL INTERPOLATION

An additional useful feature of psql
variables is that you can substitute («interpolate»)
them into regular SQL statements. The syntax for
this is again to prepend the variable name with a colon
(:).

testdb=> \set foo 'my_table'
testdb=> SELECT * FROM :foo;

would then query the table my_table. The value of
the variable is copied literally, so it can even contain unbalanced
quotes or backslash commands. You must make sure that it makes sense
where you put it. Variable interpolation will not be performed into
quoted SQL entities.

A popular application of this facility is to refer to the last
inserted OID in subsequent statements to build a
foreign key scenario. Another possible use of this mechanism is to
copy the contents of a file into a table column. First load the file into a
variable and then proceed as above.

testdb=> \set content '\'' `cat my_file.txt` '\''
testdb=> INSERT INTO my_table VALUES (:content);

One possible problem with this approach is that my_file.txt
might contain single quotes. These need to be escaped so that
they don’t cause a syntax error when the second line is processed. This
could be done with the program sed:

testdb=> \set content '\'' `sed -e "s/'/\\\\\\'/g" < my_file.txt` '\''

Observe the correct number of backslashes (6)! It works
this way: After psql has parsed this
line, it passes sed -e «s/’/\\\’/g» < my_file.txt
to the shell. The shell will do its own thing inside the double
quotes and execute sed with the arguments
-e and s/’/\\’/g. When
sed parses this it will replace the two
backslashes with a single one and then do the substitution. Perhaps
at one point you thought it was great that all Unix commands use the
same escape character. And this is ignoring the fact that you might
have to escape all backslashes as well because
SQL text constants are also subject to certain
interpretations. In that case you might be better off preparing the
file externally.

Since colons may legally appear in SQL commands, the following rule
applies: the character sequence
«:name» is not changed unless «name» is the name
of a variable that is currently set. In any case you can escape
a colon with a backslash to protect it from substitution. (The
colon syntax for variables is standard SQL for
embedded query languages, such as ECPG.
The colon syntax for array slices and type casts are
PostgreSQL extensions, hence the
conflict.)
 

PROMPTING

The prompts psql issues can be customized
to your preference. The three variables PROMPT1,
PROMPT2, and PROMPT3 contain strings
and special escape sequences that describe the appearance of the
prompt. Prompt 1 is the normal prompt that is issued when
psql requests a new command. Prompt 2 is
issued when more input is expected during command input because the
command was not terminated with a semicolon or a quote was not closed.
Prompt 3 is issued when you run an SQL
COPY command and you are expected to type in the
row values on the terminal.

The value of the selected prompt variable is printed literally,
except where a percent sign (%) is encountered.
Depending on the next character, certain other text is substituted
instead. Defined substitutions are:

%M

The full host name (with domain name) of the database server,
or [local] if the connection is over a Unix
domain socket, or
[local:/dir/name],
if the Unix domain socket is not at the compiled in default
location.

%m

The host name of the database server, truncated at the
first dot, or [local] if the connection is
over a Unix domain socket.

%>

The port number at which the database server is listening.

%n

The database session user name. (The expansion of this
value might change during a database session as the result
of the command SET SESSION
AUTHORIZATION.)

%/

The name of the current database.

%~

Like %/, but the output is ~
(tilde) if the database is your default database.

%#

If the session user is a database superuser, then a
#, otherwise a >.
(The expansion of this value might change during a database
session as the result of the command SET SESSION
AUTHORIZATION.)

%R

In prompt 1 normally =, but ^ if
in single-line mode, and ! if the session is
disconnected from the database (which can happen if
\connect fails). In prompt 2 the sequence is
replaced by -, *, a single quote,
a double quote, or a dollar sign, depending on whether
psql expects more input because the
command wasn’t terminated yet, because you are inside a
/* … */ comment, or because you are inside
a quoted or dollar-escaped string. In prompt 3 the sequence doesn’t
produce anything.

%x

Transaction status: an empty string when not in a transaction
block, or * when in a transaction block, or
! when in a failed transaction block, or ?
when the transaction state is indeterminate (for example, because
there is no connection).

%digits

The character with the indicated octal code is substituted.

%:name:

The value of the psql variable
name. See the
section Variables [psql(1)] for details.

%`command`

The output of command, similar to ordinary
«back-tick» substitution.

%[ … %]

Prompts may contain terminal control characters which, for
example, change the color, background, or style of the prompt
text, or change the title of the terminal window. In order for
the line editing features of Readline to work properly, these
non-printing control characters must be designated as invisible
by surrounding them with %[ and
%]. Multiple pairs of these may occur within
the prompt. For example,

testdb=> \set PROMPT1 '%[%033[1;33;40m%]%n@%/%R%[%033[0m%#%] '

results in a boldfaced (1;) yellow-on-black
(33;40) prompt on VT100-compatible, color-capable
terminals.

To insert a percent sign into your prompt, write
%%. The default prompts are
‘%/%R%# ‘ for prompts 1 and 2, and
‘>> ‘ for prompt 3.

Note:

This feature was shamelessly plagiarized from
tcsh.

COMMAND-LINE EDITING

psql supports the Readline
library for convenient line editing and retrieval. The command
history is automatically saved when psql
exits and is reloaded when
psql starts up. Tab-completion is also
supported, although the completion logic makes no claim to be an
SQL parser. If for some reason you do not like the tab completion, you
can turn it off by putting this in a file named
.inputrc in your home directory:

$if psql
set disable-completion on
$endif

(This is not a psql but a
Readline feature. Read its documentation
for further details.)
 

ENVIRONMENT

PAGER

If the query results do not fit on the screen, they are piped
through this command. Typical values are
more or less. The default
is platform-dependent. The use of the pager can be disabled by
using the \pset command.

PGDATABASE

Default connection database

PGHOST

PGPORT

PGUSER

Default connection parameters

PSQL_EDITOR

EDITOR

VISUAL

Editor used by the \e command. The variables
are examined in the order listed; the first that is set is used.

SHELL

Command executed by the \! command.

TMPDIR

Directory for storing temporary files. The default is
/tmp.

FILES

*

Before starting up, psql attempts to
read and execute commands from the system-wide
psqlrc file and the user’s
~/.psqlrc file.
(On Windows, the user’s startup file is named
%APPDATA%\postgresql\psqlrc.conf.)
See PREFIX/share/psqlrc.sample
for information on setting up the system-wide file. It could be used
to set up the client or the server to taste (using the \set
and SET commands).

*

Both the system-wide psqlrc file and the user’s
~/.psqlrc file can be made version-specific
by appending a dash and the PostgreSQL
release number, for example ~/.psqlrc-8.1.11.
A matching version-specific file will be read in preference to a
non-version-specific file.

*

The command-line history is stored in the file
~/.psql_history, or
%APPDATA%\postgresql\psql_history on Windows.

NOTES

*

In an earlier life psql allowed the
first argument of a single-letter backslash command to start
directly after the command, without intervening whitespace. For
compatibility this is still supported to some extent,
but we are not going to explain the details here as this use is
discouraged. If you get strange messages, keep this in mind.
For example

testdb=> \foo
Field separator is "oo".

which is perhaps not what one would expect.

*

psql only works smoothly with servers
of the same version. That does not mean other combinations will
fail outright, but subtle and not-so-subtle problems might come
up. Backslash commands are particularly likely to fail if the
server is of a different version.

NOTES FOR WINDOWS USERS

psql is built as a «console
application». Since the Windows console windows use a different
encoding than the rest of the system, you must take special care
when using 8-bit characters within psql.
If psql detects a problematic
console code page, it will warn you at startup. To change the
console code page, two things are necessary:

*

Set the code page by entering cmd.exe /c chcp
1252. (1252 is a code page that is appropriate for
German; replace it with your value.) If you are using Cygwin,
you can put this command in /etc/profile.

*

Set the console font to «Lucida Console», because the
raster font does not work with the ANSI code page.

EXAMPLES

The first example shows how to spread a command over several lines of
input. Notice the changing prompt:

testdb=> CREATE TABLE my_table (
testdb(>  first integer not null default 0,
testdb(>  second text)
testdb-> ;
CREATE TABLE

Now look at the table definition again:

testdb=> \d my_table
             Table "my_table"
 Attribute |  Type   |      Modifier
-----------+---------+--------------------
 first     | integer | not null default 0
 second    | text    |

Now we change the prompt to something more interesting:

testdb=> \set PROMPT1 '%n@%m %~%R%# '
peter@localhost testdb=>

Let’s assume you have filled the table with data and want to take a
look at it:

peter@localhost testdb=> SELECT * FROM my_table;
 first | second
-------+--------
     1 | one
     2 | two
     3 | three
     4 | four
(4 rows)

You can display tables in different ways by using the
\pset command:

peter@localhost testdb=> \pset border 2
Border style is 2.
peter@localhost testdb=> SELECT * FROM my_table;
+-------+--------+
| first | second |
+-------+--------+
|     1 | one    |
|     2 | two    |
|     3 | three  |
|     4 | four   |
+-------+--------+
(4 rows)

peter@localhost testdb=> \pset border 0
Border style is 0.
peter@localhost testdb=> SELECT * FROM my_table;
first second
----- ------
    1 one
    2 two
    3 three
    4 four
(4 rows)

peter@localhost testdb=> \pset border 1
Border style is 1.
peter@localhost testdb=> \pset format unaligned
Output format is unaligned.
peter@localhost testdb=> \pset fieldsep ","
Field separator is ",".
peter@localhost testdb=> \pset tuples_only
Showing only tuples.
peter@localhost testdb=> SELECT second, first FROM my_table;
one,1
two,2
three,3
four,4

Alternatively, use the short commands:

peter@localhost testdb=> \a \t \x
Output format is aligned.
Tuples only is off.
Expanded display is on.
peter@localhost testdb=> SELECT * FROM my_table;
-[ RECORD 1 ]-
first  | 1
second | one
-[ RECORD 2 ]-
first  | 2
second | two
-[ RECORD 3 ]-
first  | 3
second | three
-[ RECORD 4 ]-
first  | 4
second | four

SEE ALSO

Environment Variables (the documentation)

Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXIT STATUS

USAGE

CONNECTING TO A DATABASE

ENTERING SQL COMMANDS

META-COMMANDS

ADVANCED FEATURES

VARIABLES

SQL INTERPOLATION

PROMPTING

COMMAND-LINE EDITING

ENVIRONMENT

FILES

NOTES

NOTES FOR WINDOWS USERS

EXAMPLES

SEE ALSO

Материал из Кафедра ИУ5 МГТУ им. Н.Э.Баумана, студенческое сообщество

В статье пойдёт речь о том, как добиться корректного вывода кириллицы в «консоли» Windows (cmd.exe).

Описание проблемы

В дистрибутив PostgreSQL, помимо всего прочего, для работы с СУБД входит:

• приложение с графическим интерфейсом pgAdmin;
• консольная утилита psql.

При работе с psql в среде Windows пользователи всегда довольно часто сталкиваются с проблемой вывода кириллицы. Например, при отображении результатов запроса к таблице, в полях которых хранятся строковые данные на русском языке.

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Ну и зачем тогда работать с psql, кому нужно долбить клавиатурой в консольке, когда можно всё сделать красиво и быстро в pgAdmin? Ну, не всегда pgAdmin доступен, особенно если речь идёт об удалённой машине. Кроме того, выполнение SQL-запросов в текстовом режиме консоли — это +10 к хакирству.

Решение проблемы

Версии ПО:

• MS Windows 7 SP1 x64;
• PostgreSQL 8.4.12 x32.

На сервере имеется БД, созданная в кодировке UTF8.

Суть

Суть проблемы в том, что cmd.exe работает (и так будет до скончания времён) в кодировке CP866, а сама Windows — в WIN1251, о чём psql предупреждает при начале работы:

WARNING: Console code page (866) differs from Windows code page (1251)
         8-bit characters might not work correctly. See psql reference
         page "Notes for Windows users" for details.

Значит, надо как-то добиться, чтобы кодировка была одна.

В разных источниках встречаются разные рецепты, включая правку реестра и подмену файлов в системных папках Windows. Ничего этого делать не нужно, достаточно всего трёх шагов:

1. сменить шрифт у cmd.exe;
2. сменить текущую кодовую страницу cmd.exe;
3. сменить кодировку на стороне клиента в psql.

Конкретные действия

Супер быстро и просто

Запускаете cmd.exe, оттуда psql:

psql -d ВАШАБАЗА -U ВАШЛОГИН

Далее:

psql \! chcp 1251

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Быстро и просто

Запускаете cmd.exe, оттуда psql:

psql -d ВАШАБАЗА -U ВАШЛОГИН

Вводите пароль (если установлен) и выполняете команду:

set client_encoding='WIN866';

И всё. Теперь результаты запроса, содержащие кириллицу, будут отображаться нормально. Но есть небольшой косяк:

Картинка с сайта: iu5bmstu.ru

Потому предлагаем ещё способ, который этого недостатка лишён.

Посложнее и подольше

Запустить cmd.exe, нажать мышью в правом левом верхнем углу окна, там Свойства — Шрифт — выбрать Lucida Console. Нажать ОК.

Выполнить команду:

chcp 1251

В ответ выведет:

Текущая кодовая страница: 1251

Запустить psql;

psql -d ВАШАБАЗА -U ВАШЛОГИН

Кстати, обратите внимание — теперь предупреждения о несовпадении кодировок нет.

Выполнить:

set client_encoding='win1251';

Он выведет:

SET

Всё, теперь кириллица будет нормально отображаться.

Проверяем:

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