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What MySQL COUNT() function returns if there are some NULL values stored in a column also?
When we use MySQL COUNT() function to count the values stored in a column which also stored some NULL values then MySQL ignores the NULL and returns the result for only non-NULL values. To understand it, we are using the data, as follows, from table ‘Employee’ −
mysql> Select * from Employee; +----+--------+--------+ | ID | Name | Salary | +----+--------+--------+ | 1 | Gaurav | 50000 | | 2 | Rahul | 20000 | | 3 | Advik | 25000 | | 4 | Aarav | 65000 | | 5 | Ram | 20000 | | 6 | Mohan | 30000 | | 7 | Aryan | NULL | | 8 | Vinay | NULL | +----+--------+--------+ 8 rows in set (0.00 sec)
Now, the following query applies COUNT() function on column ‘Salary’ −
mysql> Select COUNT(salary) from employee568; +---------------+ | COUNT(salary) | +---------------+ | 6 | +---------------+ 1 row in set (0.15 sec)
From the above result set, it is clear that MySQL ignores NULL and returns the count for only non-NULL values.
Updated on: 22-Jun-2020
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