Question

我有2个表emp和salgrade，其架构定义为： emp（empno，ename，sal，mgr）和salgrade（grade，losal，hisal）

查询

列出在国王下工作的最高级的英雄，等级超过3。

我已经按照以下说明编写了这个，首先提取所有在KING下工作的员工，等级> 3，然后从中提取最资深的员工及其雇员，但它给我语法错误，而不是单一组-group功能，请指导我哪里做错了？

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Answer 1

添加Group by以查找每个Hiredate

的最低ename

SELECT ename, 
       Min(hiredate) 
FROM   (SELECT ename, 
               hiredate 
        FROM   emp, 
               salgrade 
        WHERE  mgr = (SELECT empno 
                      FROM   emp 
                      WHERE  ename = 'KING') 
               AND salgrade.grade > 3 
               AND emp.sal BETWEEN salgrade.losal AND salgrade.hisal) 
GROUP  BY ename  --Here

查询可以像这样简化

SELECT ename, 
       Min(hiredate) 
FROM   emp 
       JOIN salgrade 
         ON mgr = empno 
            AND emp.sal BETWEEN salgrade.losal AND salgrade.hisal 
WHERE  ename = 'KING' 
       AND salgrade.grade > 3 
GROUP  BY ename

更新：要查找最资深的员工，请使用Order by和ROWNUM

SELECT * 
FROM   (SELECT * 
        FROM   emp 
               join salgrade 
                 ON mgr = empno 
                    AND emp.sal BETWEEN salgrade.losal AND salgrade.hisal 
        WHERE  ename = 'KING' 
               AND salgrade.grade > 3 
        ORDER  BY hiredate ASC) 
WHERE  ROWNUM = 1

为什么聚合函数不适用于以下查询的内联视图？

1 个答案: