SQL Filter results using WHERE and HAVING WHERE clause with NULL/NOT NULL values
Example
SELECT *
FROM Employees
WHERE ManagerId IS NULL
This statement will return all Employee records where the value of the ManagerId column is NULL.
The result will be:
Id FName LName PhoneNumber ManagerId DepartmentId
1 James Smith 1234567890 NULL 1
SELECT *
FROM Employees
WHERE ManagerId IS NOT NULL
This statement will return all Employee records where the value of the ManagerId is not NULL.
The result will be:
Id FName LName PhoneNumber ManagerId DepartmentId
2 John Johnson 2468101214 1 1
3 Michael Williams 1357911131 1 2
4 Johnathon Smith 1212121212 2 1
Note: The same query will not return results if you change the WHERE clause to WHERE ManagerId = NULL or WHERE ManagerId <> NULL.
