以下哪个SQL语句可以正确地计算每个部门的员工数量？

A.SELECT COUNT(*) FROM employees

B.SELECT COUNT(*) FROM employees GROUP BY department_id

C.SELECT COUNT(department_id) FROM employees

D.SELECT SUM(department_id) FROM employees

优质解答

GROUP BY department_id后，COUNT(*)统计每个小组的记录数目，即每个部门的员工数。

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