Question

我一直在用砖墙砸我的头试图让这个工作，我不知道为什么不这样做。

我使用my_field连接表A和B.然后我运行一个子查询来从表B 获取my_field，其中complete = 1 。这就是我想用来查询表C和D

的内容

这是我当前的查询

SELECT 
    table_A.*,
    table_B.*,
    table_C.*,
    table_D.*
FROM table_A
    INNER JOIN table_B ON
        table_A.my_field = table_B.my_field
    LEFT JOIN (SELECT my_field FROM table_B WHERE complete ='1') test ON
        table_B.my_field = test.my_field
    RIGHT JOIN table_C ON
        test.my_field = table_C.my_field
    INNER JOIN table_D ON
        table_C.my_field = table_D.my_field

这是当前查询的输出

table_A.field1  |   table_A.field2  |   table_B.field1  |   table_B.field2  |   table_C.field1  |   table_C.field2  |   table_D.field1  |   table_D.field2  |   test.complete
=============================================================================================================================================================================
something       |   something       |   something       |   something       |   something       |   something       |   something       |   something       |       1
    null        |       null        |       null        |       null        |   something       |   something       |   something       |   something       |       0

这就是我想要的

table_A.field1  |   table_A.field2  |   table_B.field1  |   table_B.field2  |   table_C.field1  |   table_C.field2  |   table_D.field1  |   table_D.field2  |   test.complete
=============================================================================================================================================================================
something       |   something       |   something       |   something       |   something       |   something       |   something       |   something       |       1
something       |   something       |   something       |   something       |   null            |   null            |   null            |       null        |       0

更新：

这是表格结构。我删除了没有链接到任何其他表的列

CREATE TABLE IF NOT EXISTS `table_A` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `code` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `code` (`code`)
);

CREATE TABLE IF NOT EXISTS `table_B` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `code` varchar(255) NOT NULL,
  `complete` enum('0','1') NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`)
);

CREATE TABLE IF NOT EXISTS `table_C` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `code` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `code` (`code`)
);

CREATE TABLE IF NOT EXISTS `table_D` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `code` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
);

Answer 1

为什么不摆脱左联盟？这使得阅读更容易。

SELECT 
  table_A.*,
  table_B.*,
  table_C.*,
  table_D.*
FROM table_A
  INNER JOIN table_B ON
    table_A.my_field = table_B.my_field
  LEFT JOIN table_C ON
    table_B.my_field = table_C.my_field and table_B.complete ='1'
  LEFT JOIN table_D ON
    table_C.my_field = table_D.my_field

MySQL连接表提供了意外的输出

1 个答案: