postgresql cheatsheet.md

POSTGRESQL CHEATSHEET

Basic commands

psql -U postgres

Some interesting flags (to see all, use -h or --help depending on your psql version):

• -E: will describe the underlaying queries of the \ commands (cool for learning!)
• -l: psql will list all databases and then exit (useful if the user you connect with doesn't has a default database, like at AWS RDS)

Most \d commands support additional param of __schema__.name__ and accept wildcards like *.*

• \q: Quit/Exit
• \c __database__: Connect to a database
• \d __table__: Show table definition including triggers
• \d+ __table__: More detailed table definition including description and physical disk size
• \l: List databases
• \dy: List events
• \df: List functions
• \di: List indexes
• \dn: List schemas
• \dt *.*: List tables from all schemas (if *.* is omitted will only show SEARCH_PATH ones)
• \dT+: List all data types
• \dv: List views
• \df+ __function__ : Show function SQL code.
• \x: Pretty-format query results instead of the not-so-useful ASCII tables
• \copy (SELECT * FROM __table_name__) TO 'file_path_and_name.csv' WITH CSV: Export a table as CSV

User Related:

• \du: List users
• \du __username__: List a username if present.
• create role __test1__: Create a role with an existing username.
• create role __test2__ noinherit login password __passsword__;: Create a role with username and password.
• set role __test__;: Change role for current session to __test__.
• grant __test2__ to __test1__;: Allow __test1__ to set its role as __test2__.

Configuration

• Service management commands:

sudo service postgresql stop
sudo service postgresql start
sudo service postgresql restart

CRUD – Create Read Update Delete

Create – Creating table & inserting the values.

• DB Creation

createdb 'projectx'

• Table creation

CREATE TABLE users (name, age, birthday);

• Add values to table

INSERT INTO users (name, age, birthday) VALUES ('Smith', 69, '2000-12-18');

Read – Retrieve table data.

• Retrieve all table data

SELECT * FROM users

• Retrive all data with some conditional

SELECT * FROM users WHERE name LIKE 'B%';

• Retrive all data and sort

SELECT * FROM users ORDER BY score DESC;

SELECT * FROM users ORDER BY score ASC;

Update - Update table data.

• Update table values

UPDATE users SET age=10 WHERE name='Bolaji';

• Update table column

ALTER TABLE users ADD score smallint;

• Update multiple row values

UPDATE users SET score = 50 WHERE name ='Bolaji' OR name='Sally';

Delete - Delete table data.

DELETE FROM users WHERE name=Bolaji;

DROP TABLE users;

SQL Functions

SELECT AVG(score) FROM users;

SELECT SUM(score) FROM users;

SELECT COUNT(score) FROM users;

---

CREATE TABLE login (
          ID serial NOT NULL PRIMARY KEY,
          secret VARCHAR (100) NOT NULL,
          name text UNIQUE NOT NULL
);

INSERT INTO login (secret, name) values ('123abbc', 'Bolaji');

SELECT * FROM users JOIN login ON users.name = login.name;