Consider the Employees table below.
Next POst, we have learned to write a LEFT OUTER SELF JOIN query, which produced the following output.
In the output, the MANAGER column, for Todd's rows is NULL. I want to replace the NULL value, with 'No Manager'
Replacing NULL value using ISNULL() function: We are passing 2 parameters to IsNull() function. If M.Name returns NULL, then the 'No Manager' string is used as the replacement value.
SELECT E.Name as Employee, ISNULL(M.Name,'No Manager') as Manager
FROM tblEmployee E
LEFT JOIN tblEmployee M
ON E.ManagerID = M.EmployeeID
Replacing NULL value using CASE Statement:
SELECT E.Name as Employee, CASE WHEN M.Name IS NULL THEN 'No Manager'
ELSE M.Name END as Manager
FROM tblEmployee E
LEFT JOIN tblEmployee M
ON E.ManagerID = M.EmployeeID
Replacing NULL value using COALESCE() function: COALESCE() function, returns the first NON NULL value.
SELECT E.Name as Employee, COALESCE(M.Name, 'No Manager') as Manager
FROM tblEmployee E
LEFT JOIN tblEmployee M
ON E.ManagerID = M.EmployeeID
