Question

我知道这些问题很多，但我无法在其他地方找到明确的答案。

我有4张桌子：

person_per
person2group2role_p2g2r
group_grp
list_lst

我想运行查询，显示有关某人的所有信息，包括他们所在的群组类型

per_ID位于person_per表

中

多对多网桥包含per_ID，grp_ID和role_ID

grp_ID位于group_grp表

中

grp_type表格中的group_grp与lst_optionID

选项1：

SELECT person_per.per_ID as AddToCart, CONCAT(person_per.per_FirstName, ' ', person_per.per_MiddleName) AS 'FirstNames', person_per.per_LastName AS 'Surname', 
    (SELECT lst_OptionName FROM list_lst WHERE list_lst.lst_ID=1 AND
        list_lst.lst_OptionID=person_per.per_cls_ID) AS "Classification",
    person_per.per_HomePhone AS 'Tel', person_per.per_WorkPhone AS 'Cell',
    person_per.per_Email AS 'Email',
    --START DIFF
    (SELECT lst_OptionName 
    FROM list_lst, person2group2role_p2g2r, group_grp, person_per 
    WHERE list_lst.lst_ID=3 
        AND person_per.per_ID = person2group2role_p2g2r.p2g2r_per_ID 
        AND person2group2role_p2g2r.p2g2r_grp_ID = group_grp.grp_ID 
        AND group_grp.grp_Type = list_lst.lst_ID) AS "LifeGroupType"
    --END DIFF
FROM person_per
ORDER BY person_per.per_LastName

选项2：

SELECT person_per.per_ID as AddToCart, CONCAT(person_per.per_FirstName, ' ', person_per.per_MiddleName) AS 'FirstNames', person_per.per_LastName AS 'Surname',
    (SELECT lst_OptionName FROM list_lst WHERE list_lst.lst_ID=1 AND
        list_lst.lst_OptionID=person_per.per_cls_ID) AS "Classification",
    person_per.per_HomePhone AS 'Tel', person_per.per_WorkPhone AS 'Cell',
    person_per.per_Email AS 'Email',
    --START DIFF
    (SELECT lst_OptionName 
    FROM list_lst 
        JOIN group_grp ON group_grp.grp_Type = list_lst.lst_ID
        JOIN person2group2role_p2g2r ON person2group2role_p2g2r.p2g2r_grp_ID = group_grp.grp_ID
        JOIN person_per ON person_per.per_ID = person2group2role_p2g2r.p2g2r_per_ID
    WHERE list_lst.lst_ID=3) AS "LifeGroupType"
    --END DIFF
FROM person_per
ORDER BY person_per.per_LastName

我知道这是一个问题，因为每个人都可以分配到多个群组，我只是想知道如何分割不同的群组。优先结果将是每人一行，包括他们所有的信息以及他们所在的组。否则我将如何

将多个子查询结果CONCAT到单个字段
为该人的不同群体设置不同的行

任何信息都会令人惊叹：）

Answer 1

我将假设问题是子查询返回多行，因为每个表中有多个项目。然后，我将假设您正在使用MySQL。解决方案是一个名为group_concat()的函数：

SELECT p.per_ID as AddToCart, CONCAT(p.per_FirstName, ' ', p.per_MiddleName) AS FirstNames, 
       p.per_LastName AS Surname, 
       (SELECT group_concat(lst_OptionName)
        FROM list_lst l
        WHERE l.lst_ID = 1 AND l.lst_OptionID = p.per_cls_ID
       ) AS Classification,
       p.per_HomePhone AS Tel, p.per_WorkPhone AS Cell, p.per_Email AS Email,
    --START DIFF
       (SELECT lst_OptionName 
        FROM person2group2role_p2g2r p2g join
             group_grp g
             on p2g.p2g2r_grp_ID = g.grp_ID join
             list_lst l
             on g.grp_Type = l.lst_ID
        WHERE l.lst_ID = 3 and p.per_ID = p2g.p2g2r_per_ID
       ) AS LifeGroupType
    --END DIFF
FROM person_per p
ORDER BY p.per_LastName;

在此过程中，我还添加了表别名，以使查询更具可读性，显式join语法，并删除子查询中对person_per的额外不必要的引用。这可能是你问题的原因。

Answer 2

您在子查询中选择了多个值，而应该只有一个。

尝试在子查询中使用LIMIT 1将解决它。或者你必须选择你需要的值，但它必须是一个值。

  SELECT person_per.per_ID as AddToCart         ,       (SELECT .......)
            ^^^^^^^^^^^^^--- you selecting 1value here     ^^^^^^
                                                         |____you should select here also one value

如何解析返回超过1行的子查询

选项1：

选项2：

2 个答案: