过滤数据：WHERE
SELECT * FROM employees
WHERE department_id = 90;
mysql> SELECT * FROM employees -> WHERE department_id = 90; +-------------+------------+-----------+----------+--------------+------------+---------+----------+----------------+------------+---------------+ | employee_id | first_name | last_name | email | phone_number | hire_date | job_id | salary | commission_pct | manager_id | department_id | +-------------+------------+-----------+----------+--------------+------------+---------+----------+----------------+------------+---------------+ | 100 | Steven | King | SKING | 515.123.4567 | 1987-06-17 | AD_PRES | 24000.00 | NULL | NULL | 90 | | 101 | Neena | Kochhar | NKOCHHAR | 515.123.4568 | 1989-09-21 | AD_VP | 17000.00 | NULL | 100 | 90 | | 102 | Lex | De Haan | LDEHAAN | 515.123.4569 | 1993-01-13 | AD_VP | 17000.00 | NULL | 100 | 90 | +-------------+------------+-----------+----------+--------------+------------+---------+----------+----------------+------------+---------------+ 3 rows in set (0.00 sec)