PostgreSQL – WHERE Clause

A WHERE clause is used in a Select statement to filter the results based on conditions specified in the ‘WHERE’ clause.

Consider an employee table as shown below:

id	first_name	last_name	department	salary
101	bryan	walker	sales	50,000
102	alex	carpenter	accounts	55,000
103	sam	white	sales	60,000
104	john	barry	sales	54,000
105	bill	wood	accounts	65,000
106	robert	hopkins	support	70,000
107	david	lee	support	72,000
108	jack	sears	support	65,000
109	tom	young	sales	55,000

Below is the SQL query to return all rows from the employee table.

SELECT * FROM employee;

id first_name last_name department salary
--- --------- --------- ---------- -------
101 bryan      walker    sales      50000
102 alex       carpenter accounts   55000
.
.
.

Let’s assume you need to view the details of only the employees who work in the ‘sales’ department. To filter the rows, you would use the ‘WHERE’ clause as shown below:

SELECT * FROM employee WHERE department='sales';

id first_name last_name department salary
--- --------- --------- ---------- -------
101 bryan      walker    sales      50000
103 sam        white     sales      60000
104 john       barry     sales      54000