Question

我的查询是

SELECT C.id, C.title, C.short_description,C.rating,C.image,C.duration,C.difficulty ,  
0 AS active , if(G.theme_id = 3,1,0) as orderField
FROM tblIdeas C
INNER JOIN tblIdeas_themes G on (G.Idea_id = C.id )
AND C.category_id = 2  and C.published = 1 and C.DELETED=0 and C.id != 4 
ORDER BY active DESC , orderField DESC ,title ASC

 tblideas ------ id,description , etc
    tblideas_themes    -------- idea_id , theme_id
    tblthemes -------------id , theme_name

在tblideas_themes中我有一个有多个主题的想法。

我希望如果想法属于特定主题，则订单字段应为1，否则订单字段应为0

问题是我得到重复的行e，g

Idea 1 ---------- with orderField 1 --as it was in that theme
Idea 1 -----------with order field 0 as ---it was also in the other theme as well

我希望列表中只有一个想法。

如果这个想法属于多个主题，那么我想要获得属于该主题的行，其中orderfield = 1。但如果想法不属于那个主题，那么我想得到orderfield = 0

的任何其他行

Answer 1

您可以使用GROUP BY将每个想法的行减少到一行。

使用OUTER JOIN加入主题表，并将theme_id = 3条件添加到连接表达式。因此，如果找到theme_id = 3的主题，orderField将为1.如果找不到theme_id = 3的主题，那么由于外连接它将为null，orderField将默认为0。

SELECT C.id, C.title, C.short_description, C.rating, C.image, C.duration, 
    C.difficulty, 0 AS active, IF(G.theme_id = 3,1,0) as orderField
FROM tblIdeas C
LEFT OUTER JOIN tblIdeas_themes G ON (G.Idea_id = C.id AND G.theme_id = 3)
WHERE C.category_id = 2  and C.published = 1 and C.DELETED=0 and C.id != 4 
GROUP BY C.id
ORDER BY active DESC , orderField DESC ,title ASC

需要帮助mysql重复行问题

1 个答案: