1z0-071 Oracle Database 12c SQL 第42题 DROP语句
Q42.
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.
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.
Correct Answer: BDE