Evaluate the following SQL statement:
ALTER TABLE hr.emp
SET UNUSED (mgr_id);
Which statement is true regarding the effect of the above SQL statement?
A.
Any synonym existing on the EMP table would have to be re-created.
B.
Any constraints defined on the MGR_ID column would be removed by the above command.
C.
Any views created on the EMP table that include the MGR_ID column would have to be dropped and re- created.
D.
Any index created on the MGR_ID column would continue to exist until the DROP UNUSED COLUMNS command is executed.
this is duplicated with question 61. and duplicated error.
I can confirm, the question should have a “Choose two” at the end since both B and C are correct. Obviously the constraints are removed (Answer B) and setting the column unused will make any view including MGR_ID invalid and not able to be corrected with an ALTER VIEW COMPILE.
Don’t need to drop and create, you can user “OR REPLACE” to remove “MGR_ID”
C is incorrect. No views can no longer use the MGR_ID, after it is unused. No new views can use this column.
You say yourself: No views can no longer use the MGR_ID, after it is unused.
So C is correct.
I did tests myself – I set a column UNUSED. Then I had to drop view first and then create it again in order to get get valid view.
B