Important Meta Commands in PostgreSQL

\c database name [username]

• to connect to a database

\l

• will return you the list of available databases

\du

• will return you the list of databases users

\dt

• will return you the list of tables in connected database

\d table name

• will returns you the structure of the given table

\e

• opens the sql query in editor or opens an editor to write query

show port

• will returns you the port no on which postgres is running

few notations which are supposed to use while parsing these inputs :

• -d : database name
• -U : User name
• -h : Host name
• -p : Port No.
• -f : File name (sql)
• -w : Password

Working with Duplicate Rows in SQL

Duplicate Rows :

• The default display of queries is all rows, including duplicate rows
• postgres=# select deptno from emp;
  deptno
  --------
  20
  30
  30
  20
  30
  30
  10
  20
  10
  30
  20
  30
  20
  10
  (14 rows)

Selecting Unique Rows (Deleting Duplicates) :

• postgres=# select distinct deptno from emp;

deptno
--------
10
20
30
(3 rows)