Question

我正在使用这个mysql查询。这里md.designation =“地区主席”等于许多记录，但返回的数据是与其相关的第一个记录中的每一个。确切地说，共有5个“地区主席”和48个俱乐部。我想返回所有俱乐部的数据，区域主席对相关俱乐部重复。

SELECT m.member_name name,md.designation, cd.club_name club, 
m.mobile mobile,cd.dues dues FROM member m,club_dues cd, 
member_designation md,member_repeat_designation mrd 
where md.designation ="Region Chairperson"  and cd.id =m.club_name 
and mrd.designation = md.id and mrd.parent_id = m.id

我无法弄清楚我做错了什么。如果不清楚，我会在这里或在必要时在sqlfiddle添加数据。

Answer 1

您的查询相当于：

SELECT      m.member_name name,
            md.designation, 
            cd.club_name club, 
            m.mobile mobile,
            cd.dues dues 

FROM        member m

INNER JOIN  club_dues cd
    ON      cd.id =m.club_name 

INNER JOIN  member_repeat_designation mrd 
    ON      mrd.parent_id = m.id

INNER JOIN  member_designation md
    ON      mrd.designation = md.id 
    AND     md.designation = "Region Chairperson"

所以，只会带回“地区主席”的俱乐部，以及该俱乐部每个地区主席的一排。

要始终为每个俱乐部带回一行，您需要使用LEFT JOIN，例如：

SELECT      m.member_name name,
            md.designation, 
            cd.club_name club, 
            m.mobile mobile,
            cd.dues dues 

FROM        member m

LEFT JOIN  club_dues cd 
    ON      cd.id =m.club_name 

LEFT JOIN  member_repeat_designation mrd 
    ON      mrd.parent_id = m.id

LEFT JOIN   member_designation md
    ON      mrd.designation = md.id 
    AND     md.designation = "Region Chairperson"

现在，这会为每个成员带回一行，不论其名称如何， close 到你想要的，但不够接近。

更接近的是添加一个DISTINCT子句，只返回具有唯一列组合的行，所以：

SELECT DISTINCT
            m.member_name name,
            md.designation, 
            cd.club_name club, 
            m.mobile mobile,
            cd.dues dues 

FROM        member m

LEFT JOIN  club_dues cd 
    ON      cd.id =m.club_name 

LEFT JOIN  member_repeat_designation mrd 
    ON      mrd.parent_id = m.id

LEFT JOIN   member_designation md
    ON      mrd.designation = md.id 
    AND     md.designation = "Region Chairperson"

Answer 2

尝试此查询：

SELECT cd.club_name club,m.member_name name,md.designation,  
m.mobile mobile,cd.dues dues 
FROM member m inner join club_dues cd on cd.id =m.club_name inner join    
member_designation   md on mrd.designation = md.id inner join 
member_repeat_designation mrd on mrd.parent_id = m.id
where md.designation LIKE 'Region Chairperson'  
group by cd.club_name;

MYSQL QUERY - 仅返回第一条记录

2 个答案: