试题详情

The my_table table has an existing primary key. You want my_id to become the new primary key. Which statement will replace the old primary key with the new one?

AALTER TABLE my_table REPLACE PRIMARY KEY WITH my_id;

BALTER TABLE my_table DROP PRIMARY KEY, ADD PRIMARY KEY (my_id);

CALTER TABLE my_table DROP PRIMARY KEY; CREATE PRIMARY INDEX my_table(my_id);

DRREATE PRIMARY INDEX my_table (my_id) REPLACE PRIMARY KEY;