PostgreSQL

Getting Started

Getting started

Switch and connect

$ sudo -u postgres psql

List all databases

postgres=# \l

Connect to the database named postgres

postgres=# \c postgres

Disconnect

postgres=# \q
postgres=# \!

psql commands {.col-span-2}

Option	Example	Description
[-d] <database>	psql -d mydb	Connecting to database
-U	psql -U john mydb	Connecting as a specific user
-h -p	psql -h localhost -p 5432 mydb	Connecting to a host/port
-U -h -p -d	psql -U admin -h 192.168.1.5 -p 2506 -d mydb	Connect remote PostgreSQL
-W	psql -W mydb	Force password
-c	psql -c ‘\c postgres’ -c ‘\dt’	Execute a SQL query or command
-H	psql -c “\l+” -H postgres > database.html	Generate HTML report
-l	psql -l	List all databases
-f	psql mydb -f file.sql	Execute commands from a file
-V	psql -V	Print the psql version

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Getting help

-	-
\h	Help on syntax of SQL commands
\h DELETE	DELETE SQL statement syntax
\?	List of PostgreSQL command

Run in PostgreSQL console

PostgreSQL Working

Recon

Show version

SHOW SERVER_VERSION;

Show system status

\conninfo

Show environmental variables

SHOW ALL;

List users

SELECT rolname FROM pg_roles;

Show current user

SELECT current_user;

Show current user’s permissions

\du

Show current database

SELECT current_database();

Show all tables in database

\dt

List functions

\df <schema>

Databases

List databases

\l

Connect to database

\c <database_name>

Show current database

SELECT current_database();

Create database

CREATE DATABASE <database_name> WITH OWNER <username>;

Drop database

DROP DATABASE IF EXISTS <database_name>;

Rename database

ALTER DATABASE <old_name> RENAME TO <new_name>;

Tables

List tables, in current db

\dt

SELECT table_schema,table_name FROM information_schema.tables ORDER BY table_schema,table_name;

List tables, globally

\dt *.*.

SELECT * FROM pg_catalog.pg_tables

List table schema

\d <table_name>
\d+ <table_name>

SELECT column_name, data_type, character_maximum_length
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = '<table_name>';

Create table

CREATE TABLE <table_name>(
  <column_name> <column_type>,
  <column_name> <column_type>
);

Create table, with an auto-incrementing primary key

CREATE TABLE <table_name> (
  <column_name> SERIAL PRIMARY KEY
);

Delete table

DROP TABLE IF EXISTS <table_name> CASCADE;

Permissions

Become the postgres user, if you have permission errors

sudo su - postgres
psql

Grant all permissions on database

GRANT ALL PRIVILEGES ON DATABASE <db_name> TO <user_name>;

Grant connection permissions on database

GRANT CONNECT ON DATABASE <db_name> TO <user_name>;

Grant permissions on schema

GRANT USAGE ON SCHEMA public TO <user_name>;

Grant permissions to functions

GRANT EXECUTE ON ALL FUNCTIONS IN SCHEMA public TO <user_name>;

Grant permissions to select, update, insert, delete, on a all tables

GRANT SELECT, UPDATE, INSERT ON ALL TABLES IN SCHEMA public TO <user_name>;

Grant permissions, on a table

GRANT SELECT, UPDATE, INSERT ON <table_name> TO <user_name>;

Grant permissions, to select, on a table

GRANT SELECT ON ALL TABLES IN SCHEMA public TO <user_name>;

Columns

Add column

ALTER TABLE <table_name> IF EXISTS
ADD <column_name> <data_type> [<constraints>];

Update column

ALTER TABLE <table_name> IF EXISTS
ALTER <column_name> TYPE <data_type> [<constraints>];

Delete column

ALTER TABLE <table_name> IF EXISTS
DROP <column_name>;

Update column to be an auto-incrementing primary key

ALTER TABLE <table_name>
ADD COLUMN <column_name> SERIAL PRIMARY KEY;

Insert into a table, with an auto-incrementing primary key

INSERT INTO <table_name>
VALUES (DEFAULT, <value1>);


INSERT INTO <table_name> (<column1_name>,<column2_name>)
VALUES ( <value1>,<value2> );

Data

Select all data

SELECT * FROM <table_name>;

Read one row of data

SELECT * FROM <table_name> LIMIT 1;

Search for data

SELECT * FROM <table_name> WHERE <column_name> = <value>;

Insert data

INSERT INTO <table_name> VALUES( <value_1>, <value_2> );

Update data

UPDATE <table_name>
SET <column_1> = <value_1>, <column_2> = <value_2>
WHERE <column_1> = <value>;

Delete all data

DELETE FROM <table_name>;

Delete specific data

DELETE FROM <table_name>
WHERE <column_name> = <value>;

Users

List roles

SELECT rolname FROM pg_roles;

Create user

CREATE USER <user_name> WITH PASSWORD '<password>';

Drop user

DROP USER IF EXISTS <user_name>;

Alter user password

ALTER ROLE <user_name> WITH PASSWORD '<password>';

Schema

List schemas

\dn

SELECT schema_name FROM information_schema.schemata;

SELECT nspname FROM pg_catalog.pg_namespace;

Create schema

CREATE SCHEMA IF NOT EXISTS <schema_name>;

Drop schema

DROP SCHEMA IF EXISTS <schema_name> CASCADE;

Dates

Show current date YYYY-MM-DD

SELECT current_date;

Calculate age between two dates

SELECT age(timestamp, timestamp);

Show current time with time zone

SELECT current_time;

Make dates using integers

SELECT make_date(2021,03,25);

PostgreSQL Commands

Tables

-	-
\d <table>	Describe table
\d+ <table>	Describe table with details
\dt	List tables from current schema
\dt *.*	List tables from all schemas
\dt <schema>.*	List tables for a schema
\dp	List table access privileges
\det[+]	List foreign tables

Query buffer

-	-
\e [FILE]	Edit the query buffer (or file)
\ef [FUNC]	Edit function definition
\p	Show the contents
\r	Reset (clear) the query buffer
\s [FILE]	Display history or save it to file
\w FILE	Write query buffer to file

Informational {.row-span-4}

-	-
\l[+]	List all databases
\dn[S+]	List schemas
\di[S+]	List indexes
\du[+]	List roles
\ds[S+]	List sequences
\df[antw][S+]	List functions
\deu[+]	List user mappings
\dv[S+]	List views
\dl	List large objects
\dT[S+]	List data types
\da[S]	List aggregates
\db[+]	List tablespaces
\dc[S+]	List conversions
\dC[+]	List casts
\ddp	List default privileges
\dd[S]	Show object descriptions
\dD[S+]	List domains
\des[+]	List foreign servers
\dew[+]	List foreign-data wrappers
\dF[+]	List text search configurations
\dFd[+]	List text search dictionaries
\dFp[+]	List text search parsers
\dFt[+]	List text search templates
\dL[S+]	List procedural languages
\do[S]	List operators
\dO[S+]	List collations
\drds	List per-database role settings
\dx[+]	List extensions

S: show system objects, +: additional detail

Connection

-	-
\c [DBNAME]	Connect to new database
\encoding [ENCODING]	Show or set client encoding
\password [USER]	Change the password
\conninfo	Display information

Formatting

-	-
\a	Toggle between unaligned and aligned
\C [STRING]	Set table title, or unset if none
\f [STRING]	Show or set field separator for unaligned
\H	Toggle HTML output mode
\t [on|off]	Show only rows
\T [STRING]	Set or unset HTML <table> tag attributes
\x [on|off]	Toggle expanded output

Input/Output

-	-
\copy ...	Import/export table See also: copy
\echo [STRING]	Print string
\i FILE	Execute file
\o [FILE]	Export all results to file
\qecho [STRING]	String to output stream

Variables

-	-
\prompt [TEXT] NAME	Set variable
\set [NAME [VALUE]]	Set variable (or list all if no parameters)
\unset NAME	Delete variable

Misc

-	-
\cd [DIR]	Change the directory
\timing [on|off]	Toggle timing
\! [COMMAND]	Execute in shell
\! ls -l	List all in shell

Large Objects

• \lo_export LOBOID FILE
• \lo_import FILE [COMMENT]
• \lo_list
• \lo_unlink LOBOID

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Miscellaneous

Backup

Use pg_dumpall to backup all databases

$ pg_dumpall -U postgres > all.sql

Use pg_dump to backup a database

$ pg_dump -d mydb -f mydb_backup.sql

-	-
-a	Dump only the data, not the schema
-s	Dump only the schema, no data
-c	Drop database before recreating
-C	Create database before restoring
-t	Dump the named table(s) only
-F	Format (c: custom, d: directory, t: tar)

Use pg_dump -? to get the full list of options

Restore

Restore a database with psql

$ psql -U user mydb < mydb_backup.sql

Restore a database with pg_restore

$ pg_restore -d mydb mydb_backup.sql -c

-	-
-U	Specify a database user
-c	Drop database before recreating
-C	Create database before restoring
-e	Exit if an error has encountered
-F	Format (c: custom, d: directory, t: tar, p: plain text sql(default))

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Use pg_restore -? to get the full list of options

Remote access

Get location of postgresql.conf

$ psql -U postgres -c 'SHOW config_file'

Append to postgresql.conf

listen_addresses = '*'

Append to pg_hba.conf (Same location as postgresql.conf)

host  all  all  0.0.0.0/0  md5
host  all  all  ::/0       md5

Restart PostgreSQL server

$ sudo systemctl restart postgresql

Import/Export CSV

Export table into CSV file

\copy table TO '<path>' CSV
\copy table(col1,col1) TO '<path>' CSV
\copy (SELECT...) TO '<path>' CSV

Import CSV file into table

\copy table FROM '<path>' CSV
\copy table(col1,col1) FROM '<path>' CSV

See also: Copy

Also see

• Posgres-cheatsheet (gist.github.com)