Question

Differentiate between count() and count(*) functions in SQL with appropriate examples.

Answer 1

COUNT(*) returns the count of all rows in the table, whereas COUNT() is used with Column_Name passed as an argument and counts the number of non-NULL values in a column that is given as an argument.

Example: Table: EMPL

EMPNO	ENAME	JOB	SAL	DEPTNO
8270	JACK	SALESMAN	2985	10
8566	ALI	CLERK	9870	20
8922	AJAY	NULL	8760	30
8736	BINDU	CLERK	5643	20
8822	JOY	MANAGER	3000	10

e.g. SELECT COUNT(*) FROM EMPL;

Output

COUNT(*)

5

e.g. SELECT COUNT(JOB) FROM EMPL;

Output

COUNT(JOB)

4

Since JOB has 1 NULL value.