Question

我想要显示未显示的行，但获取错误子查询返回的行数超过1行

这很好用;

SELECT CONCAT( P.LastName, ', ', P.FirstName ) AS Name, 
(
SELECT MP.MembershipID
FROM membershipperson MP
WHERE MP.PersonID = P.PersonID
) 
AS MembershipID, PersonID
FROM `person` P

当我添加ORDER BY'MembershipID'时，如果我按ORDER BY'PersonID'，它就会失败;

SELECT CONCAT( P.LastName, ', ', P.FirstName ) AS Name, 
(
SELECT MP.MembershipID
FROM membershipperson MP
WHERE MP.PersonID = P.PersonID
) 
AS MembershipID, PersonID
FROM `person` P
ORDER BY `MembershipID` ASC

如何获取包含所有MembershipID行的列表？

Answer 1

您应该使用内部联接。像这样：

SELECT CONCAT( P.LastName, ', ', P.FirstName ) AS Name, MP.MembershipID AS MembershipID, PersonID
FROM person P, membershipperson MP
WHERE MP.PersonID = P.PersonID

Answer 2

使用子查询是否重要？您可以使用INNER JOIN编写它：

SELECT
    CONCAT( P.LastName, ', ', P.FirstName ) AS Name,
    MP.MembershipID,
    P.PersonID
FROM `person` P
INNER JOIN `membershipperson` MP ON MP.PersonID = P.PersonID
ORDER BY MP.MembershipID ASC

为什么我得到Subquery返回超过1行

2 个答案: