SQL子查询的一些例子

1、单行子查询

        select ename,deptno,sal

        from emp

        where deptno=(select deptno from dept where loc='NEW YORK')；

     2、多行子查询

        SELECT ename,job,sal

        FROM EMP

        WHERE deptno in ( SELECT deptno FROM dept WHERE dname LIKE 'A%')；

     3、多列子查询

        SELECT deptno,ename,job,sal

        FROM EMP

        WHERE (deptno,sal) IN (SELECT deptno,MAX(sal) FROM EMP GROUP BY deptno)；

     4、内联视图子查询

       (1)SELECT ename,job,sal,rownum

          FROM (SELECT ename,job,sal FROM EMP ORDER BY sal)；

       (2)SELECT ename,job,sal,rownum

          FROM ( SELECT ename,job,sal FROM EMP ORDER BY sal)

          WHERE rownum<=5；

     5、在HAVING子句中使用子查询

        SELECT deptno,job,AVG(sal) FROM EMP GROUP BY deptno,job HAVING AVG(sal)>(SELECT sal FROM EMP WHERE ename='MARTIN')；