Here we are going to use 2 Tables "Employees" and "Department".
Below is shown the "Employees" table:
| 1 |
Richard Hughes |
4/23/1945 12:00:00 AM |
1 |
1 |
343-123-2002 |
New Orleans |
950.00 |
| 2 |
Taryn Sinclair |
3/22/1980 12:00:00 AM |
2 |
2 |
232-344-8755 |
San Francisco |
800.00 |
| 3 |
Ted Horowitz |
3/31/1960 12:00:00 AM |
3 |
4 |
435-657-9068 |
New York |
700.00 |
| 4 |
Jonathan Douglas |
7/7/1971 12:00:00 AM |
3 |
4 |
323-454-7656 |
Salt Lake City |
600.00 |
| 5 |
Miranda Leigh |
7/19/1983 12:00:00 AM |
7 |
3 |
634-465-8046 |
New York |
500.00 |
| 6 |
Jana Rae |
9/23/1976 12:00:00 AM |
8 |
2 |
434-434-1254 |
Houston |
400.00 |
| 7 |
Lita Rosanna |
9/14/1982 12:00:00 AM |
4 |
6 |
565-782-1223 |
Long Island |
650.00 |
| 8 |
Colin Flooks |
12/29/1988 12:00:00 AM |
4 |
2 |
954-652-2111 |
Salt Lake City |
600.00 |
| 9 |
Anthony Frank |
2/22/1988 12:00:00 AM |
9 |
3 |
323-243-1249 |
San Francisco |
750.00 |
| 10 |
Stephanie Lynn |
7/30/1979 12:00:00 AM |
8 |
2 |
543-765-4653 |
Salt Lake City |
450.00 |
| 11 |
Jack Martin |
8/25/1985 12:00:00 AM |
NULL |
NULL |
443-324-6522 |
Austin |
500.00 |
Below is shown the "Department" table:
| 1 |
Finance |
| 2 |
Development |
| 3 |
Testing |
| 4 |
Delivery |
| 5 |
Human Resources |
| 6 |
Administration |
In the table named "Employees", Column DeptID is the Foreign Key.
In the table named "Department", Column ProductID is the Primary Key.
In the "Employees" table data, the Department Name is not available. It is available in the "Department" table.
Using the Subquery we can make that available in the SQL resultset, using the Column DeptID, which is common in both the tables.
The following SQL query acheives the above said task.
Text Editor below has the SQL Query, click the "View Result" button, to see the result.
Select Emp.EmployeeID, Emp.EmployeeName, Emp.DeptID,
(Select Department.DeptName from Department where Department.DeptID = Emp.DeptID) as DepartmentName
From Employees Emp;
Note: Here the Emp.DeptID is passed as the argument to the Subquery. For every DeptID in the Employees, the correct DeptName is retrieved.