[英]Mysql : Left Join and Inner Join in a subquery
我有3張桌子,我已經離開了,但是我想從表格3中添加一個字段,它與表格2連接在一起。
Table1
id
name
surname
table2_fk
Table2
id
entry_name
entry_code
table3_fk
Table3
id
type_name
type_desc
SELECT `Name`, `Type Description`
(SELECT
Table1.name AS `Name`,
Table1.surname AS `Surname`,
t2.entry_name AS `Entry`,
t2.entry_code AS `Entry Code`,
t3.type_name AS `Type Name`,
t3.type_desc AS `Type Description`
FROM Table1
LEFT JOIN table2 AS t2 ON Table1.table2_fk = t2.id
LEFT JOIN table3 AS t3 ON Table2.table3_fk = t3.id
) as subquery
我期望的結果是從表1和表3獲得t2內連接t3和get字段
基於我的子查詢,我希望顯示Name
和Type Description
如果你想INNER JOIN
表table2
和table3
,然后LEFT JOIN
到table1
那么這樣做:
SELECT t1.name, t.type_desc AS `Type Description`
FROM Table1 AS t1
LEFT JOIN (
SELECT t2.id, t3.type_desc
FROM table2 AS t2
INNER JOIN table3 AS t3 ON t2.table3_fk = t3.id
) AS t ON t1.table2_fk = t2.id
但這可能表達為:
SELECT t1.name, t3.type_desc AS `Type Description`
FROM Table1 AS t1
LEFT JOIN table2 AS t2 ON t1.table2_fk = t2.id
LEFT JOIN table3 AS t3 ON t2.table3_fk = t3.id
我假設你試圖將table1與table2和table3之間的內連接結果保持連接
select t1.name, t_res.type_desc from table1 t_1
left join (
select t_2.id, t_3.type_desc from table2 t_2
inner join table3 t_3 on t_2.table3_fk = t_3.id
) as t_res on t_1.table2_fk = t_2.id
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.