TIME based (Blind) Injection

For using time based SQL Injection the command that is being performed should include an WHERE clause If the condition is true sleep for 2 secs else sleep for 5 seconds

SELECT * 
FROM users 
WHERE username="sagar" AND if(database="a", sleep(2), sleep(5));
 
SELECT * 
FROM users 
WHERE username="sagar" AND if(len(database) > 2, sleep(2), sleep(5));

The parameters for the sleep() and if() function can be different based on the DB vendor