El operador IS NULL ok

A menudo es requerido recuperar que registros que en alguna columna su valor sea igual a NULL. El operador IS NULL selecciona aquellos registros que en alguna columna determinada contiene el valor NULL esto lo hace realizando una operación de igualdad mediante el operador IS NULL en lugar del operador condicional “=”

Ejemplos:

SELECT * FROM employees WHERE last_name IS NULL;

SELECT * FROM employees WHERE last_name IS NULL;

SELECT * FROM employees WHERE email IS NULL;

SELECT * FROM employees WHERE phone_number IS NULL;

SELECT * FROM employees WHERE hire_date IS NULL;

SELECT * FROM employees WHERE job_id IS NULL;

SELECT * FROM employees WHERE commission_pct IS NULL;

SELECT * FROM employees WHERE manager_id IS NULL;

SELECT * FROM employees WHERE department_id IS NULL;

SELECT * FROM employees WHERE commission_pct IS NULL;

SELECT * FROM locations;

SELECT * FROM locations WHERE state_province IS NOT NULL;

SELECT * FROM locations WHERE state_province IS NULL;