Question

在我的数据库中有一个表有3个FK到其他3个表我希望选择此表中的数据+其他3个表中的数据当FK值=其他表中的PK值时

Answer 1

SELECT  *
FROM    t1
JOIN    t2
ON      t2.id = t1.t2_id
JOIN    t3
ON      t3.id = t1.t3_id
JOIN    t4
ON      t4.id = t1.t4_id

Answer 2

SELECT t1.Field1, t2.Field2, t3.Field3, t4.Field4
FROM Table t1
    INNER JOIN Table2 t2 ON t1.ID = t2.ID
    INNER JOIN Table3 t3 ON t1.ID = t3.ID
    INNER JOIN Table4 t4 ON t1.ID = t4.ID

如果表2 - 4中的行总是不匹配，并且您希望这些记录仍然返回，则将INNER JOIN更改为LEFT JOIN

Answer 3

SELECT * FROM ParentTable as pt
LEFT JOIN table1 as t1
ON pt.t1_ID = t1.ID
LEFT JOIN table2 as t2
ON pt.t2_ID= t2.ID
LEFT JOIN table3 as t3
ON pt.t3_ID= t3.ID

即使表1,2或3中没有匹配项，也会返回记录。@ Ada和@Q将排除这些记录。

Answer 4

SELECT * FROM TBL1 T1 RIGHT JOIN TBL2 T2 ON T1.id = T2.id RGIHT加入TBL3 T3 ON T3.id = T2.id

这将返回Right表中的所有记录以及Left表中的匹配记录。

使用存储过程在DB中加入4个表？

4 个答案: