Which three statements are true about the ALTER TABLE….DROP COLUMN…. command?
A.
A column can be dropped only if it does not contain any data.
B.
A column can be dropped only if another column exists in the table.
C.
A dropped column can be rolled back.
D.
The column in a composite PRIMARY KEY with the CASCADE option can be dropped.
E.
A parent key column in the table cannot be dropped.