Every derived table must have its own alias_每...

MYSQL要求派生表要有别名

select * from mytable a; 其中a就是mytable表的别名

这是在做内联视图子查询经常碰到的问题；

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')；