兩個表的順序是否可以調換

#查詢員工名、工種號、工種名

SELECT last_name, e.job_id, job_title FROM?jobs?AS?j,?employees?AS?e WHERE e.`job_id` = j.`job_id`;

可以加篩選？

#案例1：查詢有獎金的員工名、部門名

SELECT last_name, department_name, commission_pct FROM employees e, departments d WHERE e.`department_id`=d.`department_id` AND e.`commission_pct` IS NOT NULL;

#案例2：查詢城市名中第二個字符為o的部門名和城市名

SELECT department_name, city FROM departments d,locations l WHERE d.`location_id`=l.`location_id` AND city LIKE '_o%';

可以加分組？

#案例1：查詢每個城市的部門個數

SELECT COUNT(*) 個數, city FROM departments d, locations l WHERE d.`location_id`=l.`location_id` GROUP BY city;

#案例2：查詢出有獎金的每個部門的部門名和部門的領導編號和該部門的最低工資

SELECT department_name,d.manager_id,MIN(salary) FROM departments d, employees e WHERE d.`department_id`=e.`department_id` AND commission_pct IS NOT NULL GROUP BY department_name, d.manager_id;

可以加排序？

#案例：查詢每個工種的工種名和員工的個數，并且按員工個數降序

SELECT job_title, COUNT(*) FROM employees e , jobs j WHERE e.`job_id`=j.`job_id` GROUP BY job_title ORDER BY COUNT(*) DESC;

?可以實現三表連接嗎？

#案例：查詢員工號、部門名和所在的城市

SELECT last_name,department_name,city FROM employees e,departments d,locations l WHERE e.`department_id`=d.`department_id` AND d.`location_id`=l.`location_id`

總結

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