Sql 从不同的表中查找记录

要求

查找并显示实施的所有飞行员（员工ID和姓名） “通勤”型和“普通”型飞机上的航班

解决方案

SELECT flightI_new.eid, employee_new.ename
FROM flightI_new
INNER JOIN employee_new ON flightI_new.eid = employee_new.eid
INNER JOIN plane_new ON flightI_new.pnum = plane_new.pnum
WHERE plane_new.ptype = 'Commuter' AND plane_new.ptype = 'Normal';

该代码使用或，但由于某些原因，我得到了“未返回行”

---

你知道怎么解决吗？

你的

和

不起作用，因为记录不能在同一条记录上同时包含

和
。但您应该能够使用以下内容：

SELECT flightI_new.eid, employee_new.ename
FROM flightI_new
INNER JOIN employee_new 
    ON flightI_new.eid = employee_new.eid
INNER JOIN plane_new 
    ON flightI_new.pnum = plane_new.pnum
WHERE plane_new.ptype IN ('Commuter', 'Normal')
GROUP BY flightI_new.eid, employee_new.ename
HAVING count(distinct plane_new.ptype) = 2;

SELECT distinct flightI_new."eid", employee_new."name"
FROM flightI_new
INNER JOIN employee_new 
    ON flightI_new."eid" = employee_new."eid"
INNER JOIN plane_new 
    ON flightI_new."pnum" = plane_new."pnum"
WHERE plane_new."ptype" = 'commuter'
  AND flightI_new."eid" IN (select flightI_new."eid"
                            FROM flightI_new
                            INNER JOIN employee_new 
                                ON flightI_new."eid" = employee_new."eid"
                            INNER JOIN plane_new 
                                ON flightI_new."pnum" = plane_new."pnum"
                            WHERE plane_new."ptype" = 'normal')

看

当然，您可以使用以下内容：

SELECT flightI_new.eid, employee_new.ename
FROM flightI_new
INNER JOIN employee_new 
    ON flightI_new.eid = employee_new.eid
INNER JOIN plane_new 
    ON flightI_new.pnum = plane_new.pnum
WHERE plane_new.ptype IN ('Commuter', 'Normal')
GROUP BY flightI_new.eid, employee_new.ename
HAVING count(distinct plane_new.ptype) = 2;

SELECT distinct flightI_new."eid", employee_new."name"
FROM flightI_new
INNER JOIN employee_new 
    ON flightI_new."eid" = employee_new."eid"
INNER JOIN plane_new 
    ON flightI_new."pnum" = plane_new."pnum"
WHERE plane_new."ptype" = 'commuter'
  AND flightI_new."eid" IN (select flightI_new."eid"
                            FROM flightI_new
                            INNER JOIN employee_new 
                                ON flightI_new."eid" = employee_new."eid"
                            INNER JOIN plane_new 
                                ON flightI_new."pnum" = plane_new."pnum"
                            WHERE plane_new."ptype" = 'normal')

请参见这里的错误

      WHERE plane_new.ptype = 'Commuter' AND plane_new.ptype = 'Normal';

plane_new.ptype在数据库中不能有两个东西，计算机和普通，它必须是其中之一，这就是为什么没有返回行的原因。
也许你是说别的。
在您的位置，您只能使用
或
。返回的行是那些拥有
计算机
和
正常
的人，您的
和
在这里不起作用，因为您只查看一行。在一行中加入“通勤者”和“普通人”是互斥的。好的一个：拥有count（distinct plane_new.ptype）=2；