Step 6 – Apex Developer Day - Adding a Constraint

You now have the employee data that is referenced by the APEX_TASKS.ASSIGNED_TO column but need to identify a foreign key between the tables APEX_ATASKS and APEX_EMPLOYEES. The foreign key ensures that each ASSIGNED_TO column references a valid Employee. It also ensures that an Employee cannot be deleted who has tasks assigned. Perform the following steps:

1.	Select the down arrow next to Object Browser > Browse and then select Tables.
2.	Select the APEX_TASKS table and click the Constraints tab.
3.	Click Create.
4.	Select Foreign Key for the Constraint Type. Select Cascade Delete in constraint type, ASSIGNED_TO for the Foreign Key Column, select OBE_EMPLOYEES for the Reference Table Name and select EMPLOYEE_ID from the Reference Table Column List. Then click Next .
5.	Click Finish.
6.	The constraint was created successfully. You want to also create a check constraint on the PROJECT_PRIORITY column so that the data is validated when the data is inserted or updated. Select APEX_PROJECT_LOOKUP.
7.	Click the Create section tab.
8.	Select PROJECT_PRIORITY for the Constraint of Column field and enter in ('1','2','3') for the Constraint Expression. Ensure that Check Constraint Type is selected. Then click Next.
9.	Click Finish.
10.	The constraint was created successfully. Click the Home breadcrumb.