MySQL – IS NOT NULL
Using the MySQL IS NOT NULL condition, we can verify that the expression doesn’t contain any NULL values. This statement is used with the SELECT, INSERT, UPDATE, and DELETE statements.
expression IS NOT NULL
expression – The value specified is tested to see if it is not NULL.
SELECT * FROM employees WHERE first_name IS NOT NULL;
In this case, you get the complete table “employees” as a result, because every value in the table is not NULL.