MySQL数据库中复合查询的操作详解

SELECT * FROM EMP 
WHERE (sal>500 OR job='MANAGER') 
AND ename LIKE 'J%';

SELECT * FROM EMP ORDER BY deptno asc, sal DESC;

SELECT ename, sal*12+IFNULL(comm,0) AS '年薪' 
FROM EMP 
ORDER BY 年薪 DESC;

SELECT ename, job FROM EMP 
WHERE sal = (SELECT MAX(sal) FROM EMP);

SELECT ename, sal FROM EMP 
WHERE sal > (SELECT AVG(sal) FROM EMP);

SELECT deptno, FORMAT(AVG(sal), 2), MAX(sal) 
FROM EMP 
GROUP BY deptno;

SELECT deptno, AVG(sal) AS avg_sal 
FROM EMP 
GROUP BY deptno 
HAVING avg_sal < 2000;

-- 错误示例：产生笛卡尔积
SELECT * FROM EMP, DEPT;

SELECT EMP.ename, EMP.sal, DEPT.dname 
FROM EMP, DEPT 
WHERE EMP.deptno = DEPT.deptno;

SELECT ename, sal, dname 
FROM EMP, DEPT 
WHERE EMP.deptno = DEPT.deptno 
AND DEPT.deptno = 10;

SELECT ename, sal, grade 
FROM EMP, SALGRADE 
WHERE EMP.sal BETWEEN losal AND hisal;

SELECT empno, ename 
FROM emp 
WHERE empno = (SELECT mgr FROM emp WHERE ename='FORD');

SELECT leader.empno, leader.ename 
FROM emp leader, emp worker 
WHERE leader.empno = worker.mgr 
AND worker.ename='FORD';

SELECT * FROM EMP 
WHERE deptno = (SELECT deptno FROM EMP WHERE ename='SMITH');

SELECT ename, job, sal, deptno 
FROM emp 
WHERE job IN (SELECT DISTINCT job FROM emp WHERE deptno=10) 
AND deptno != 10;

SELECT ename, sal, deptno 
FROM EMP 
WHERE sal > ALL(SELECT sal FROM EMP WHERE deptno=30);

SELECT ename, sal, deptno 
FROM EMP 
WHERE sal > ANY(SELECT sal FROM EMP WHERE deptno=30);

SELECT ename FROM EMP 
WHERE (deptno, job) = (SELECT deptno, job FROM EMP WHERE ename='SMITH') 
AND ename <> 'SMITH';

SELECT ename, deptno, sal, FORMAT(asal,2) 
FROM EMP, 
  (SELECT AVG(sal) asal, deptno dt FROM EMP GROUP BY deptno) tmp 
WHERE EMP.sal > tmp.asal AND EMP.deptno = tmp.dt;

SELECT EMP.ename, EMP.sal, EMP.deptno, ms 
FROM EMP, 
  (SELECT MAX(sal) ms, deptno FROM EMP GROUP BY deptno) tmp 
WHERE EMP.deptno = tmp.deptno AND EMP.sal = tmp.ms;

SELECT DEPT.deptno, dname, mycnt, loc 
FROM DEPT, 
  (SELECT COUNT(*) mycnt, deptno FROM EMP GROUP BY deptno) tmp 
WHERE DEPT.deptno = tmp.deptno;

SELECT ename, sal, job FROM EMP WHERE sal>2500
UNION
SELECT ename, sal, job FROM EMP WHERE job='MANAGER';

SELECT ename, sal, job FROM EMP WHERE sal>2500
UNION ALL
SELECT ename, sal, job FROM EMP WHERE job='MANAGER';