在 sql 查询中对同一张表使用两个 JOIN

Question

我有一个类似下面的查询，它工作正常。

SELECT 
    "A".id AS A_id,
    "B".id AS B_id,
    "C".id AS C_id,
    "D".id AS D_id,
    "E".id AS E_id,
    "F".id AS F_id,
    "G".id AS G_id,
    "H".id AS H_id,
    "I".id AS I_id
FROM "A" 
INNER JOIN "B" ON "A".id = "B".A_id 
INNER JOIN "C" ON "B".C_id = "C".id
INNER JOIN "D" ON "C".D_id = "D".id
INNER JOIN "E" ON "D".id = "E".D_id
INNER JOIN "F" ON "E".F_id = "F".id
INNER JOIN "G" ON "F".G_id = "G".id
INNER JOIN "H" ON "G".id = "H".G_id
INNER JOIN "I" ON "H".I_id = "I".id;

现在我想添加特殊条件。表“B”与另一个表连接 我必须添加特殊加入（完全加入），但毕竟加入。像下面的东西 （当然不行）：

SELECT 
    "A".id AS A_id,
    "B".id AS B_id,
    "C".id AS C_id,
    "D".id AS D_id,
    "E".id AS E_id,
    "F".id AS F_id,
    "G".id AS G_id,
    "H".id AS H_id,
    "I".id AS I_id,
    "Setup".id AS setup_id,
    "Run".id AS run_id
FROM "A" 
INNER JOIN "B" ON "A".id = "B".A_id 
INNER JOIN "C" ON "B".C_id = "C".id
INNER JOIN "D" ON "C".D_id = "D".id
INNER JOIN "E" ON "D".id = "E".D_id
INNER JOIN "F" ON "E".F_id = "F".id
INNER JOIN "G" ON "F".G_id = "G".id
INNER JOIN "H" ON "G".id = "H".G_id
INNER JOIN "I" ON "H".I_id = "I".id

AND FROM
"Setup" 
FULL JOIN "Run" ON "Setup".id = "Run".id
FULL JOIN "B" ON "Setup".id = "B".id;

我使用了完全连接，因为“运行”和“设置”表中的每一个都只包含一行，但与表“B”相连，该表有不止一行，我希望将它们全部放在结果表中.

如何修复？也许尝试在选择中使用选择？

Answer 1

您不需要完全联接来获得反映在您描述的一对多关系中的多行。另一个内部连接。并且没有“AND FROM”结构。您可以直接添加连接。

INNER JOIN "I" ON "H".I_id = "I".id
INNER JOIN "Setup" ON "B".id = "Setup".id;
INNER JOIN "Run" ON "Setup".id = "Run".id

您可能应该阅读joins。

[编辑]

评论表明数据是不对称的，因此您确实需要外连接，所以：

INNER JOIN "I" ON "H".I_id = "I".id
LEFT JOIN "Setup" ON "B".id = "Setup".id;
LEFT JOIN "Run" ON "Setup".id = "Run".id