A.更改employees表并禁用emp_manager_fk約束條件
B.向EMPLOYEES表添加FOREIGN KEY約束條件，要求經(jīng)理必須已是雇員
C.向EMPLOYEES表添加FOREIGN KEY約束條件，要求經(jīng)理標(biāo)識應(yīng)匹配每個(gè)雇員標(biāo)識
D.更改employees表并添加FOREIGN KEY約束，要求每個(gè)雇員標(biāo)識必須唯一

A.ALTER TABLE salary ADD CONSTRAINT fk_employee_id_01 FOREIGN KEY（employee_id）REFERENCES employees（employee_id）
B.ALTER TABLE salary ADD CONSTRAINT fk_employee_id_ FOREIGN KEY BETWEEN salary（employee_id）AND employees（employee_id）
C.ALTER TABLE salary FOREIGN KEY CONSTRAINT fk_employee_id_REFERENCES employees（employee_id）
D.ALTER TABLE salary ADD CONSTRAINT fk_employee_id_FOREIGN KEY salary（employee_id）=employees（employee_id）