psql [ option... ] [ dbname [ username ] ]
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.
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.
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.
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.
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.
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.
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.
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 8.1.0, 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 [(7)] and NOTIFY [(7)].
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:
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.
The syntax of the command is similar to that of the SQL 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.
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.
=> \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 [(7)] SQL command.
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.
If pattern is specified, only objects whose names match the pattern are listed.
The commands GRANT and REVOKE are used to set access privileges. See GRANT [(7)] for more information.
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.
=> \echo `date` Tue Oct 26 21:40:57 CEST 1999If the first argument is an unquoted -n the trailing newline is not written.
foo=> \lo_import '/home/peter/pictures/photo.xcf' 'a picture of me' lo_import 152801The 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.
``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.
Adjustable printing options are:
``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.)
Expanded mode is supported by all four output formats.
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.
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.
The commands GRANT and REVOKE are used to set access privileges. See GRANT [(7)] for more information.
This is an alias for \dp (``display privileges'').
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 *.*.
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 barsets 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
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.
\set HISTFILE ~/.psql_history- :DBNAMEin ~/.psqlrc will cause psql to maintain a separate history for each database.
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.)
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:
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.
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.)
testdb=> \foo Field separator is "oo".which is perhaps not what one would expect.
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:
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 TABLENow 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