Self Join Query

SQL Self Join Query Example

We use a self join in this update query example we want to update each employee's salary by 10%.  There are at least two ways to do this query.

Example c) (below) is supposed to work but I get errors in Access.  It is called a correlated subquery - if you can tell me what is wrong with it I'd really appreciate it.

Self Join Query Code:

a)  Update M_Employees as A INNER JOIN M_Employees as B ON A.Employee_ID = B.Employee_ID SET A.Salary = B.Salary*1.1

b)  Update M_Employees as A, M_Employees as B Set A.Salary=B.Salary * 1.1
Where A.Employee_ID=B.Employee_ID

c)  Update M_Employees as A set A.Salary = (Select Salary * 1.1 from M_Employees Where M_Employees.Employee_ID = A.Employee_ID)

Note:  I have added a another feature to this self join query example - Aliases.  Aliases are where you use 'as' to establish a short nickname for a table or a field.  This alias feature helps when you have long table names or are trying to do a correlated subquery.

Additional Update Query Information: