单选题
View the Exhibit and examine the structure of the EMP table. You executed the following command to add a primary key to the EMP table： ALTER TABLE emp ADD CONSTRAINT emp_id_pk PRIMARY KEY （emp_id） USING INDEX emp_id_idx； Which statement is true regarding the effect of the command？（）
发布日期：2022-07-17
A
The PRIMARY KEY is created along with a new index.
B
The PRIMARY KEY is created and it would use an existing unique index.
C
The PRIMARY KEY would be created in a disabled state because it is using an existing index.
D
The statement produces an error because the USING clause is permitted only in the CREATE TABLE command.
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