Question

我有两张桌子：

表公司

+----------+-------------+----+
| Id | MainId | Type   | Name | 
+----+--------+--------+------+
| 1  |        | NO     |      |
| 2  |    1   | Filial |      |
| 3  |        | NO     |      |
| 4  |    3   | Filiar |      |
+-------------+--------+------+

表员工

+------------------+-------+-------+
| Id | Name        | CompId| FilId |
+------------------+-------+-------+
| 333| Simon       | 1     |       |
| 444| John        | 1     | 2     |
| 555| Andrew      |       | 4     |
| 777| Dennis      | 11    |       |
| 888| John        | 3     | 10    |
+------------------+-------+-------+

如何让所有在公司表中列出的公司工作的员工？ =至少有一行（CompId或FilId）链接到公司表
如何让所有不在公司表中列出的公司工作的员工？ =公司表中不存在CompId或FilId列

我已尝试过该解决方案，但效果不佳...

第一

SELECT * FROM `Employees`  
INNER JOIN `Companies` ON `Employees`.`FilId` = `Companies`.`Id` 
OR `Employees`.`FilId` = `Companies`.`Id`

为SHOW CREATE TABLE table_name添加了结果删除了未使用的列

CREATE TABLE `Employees` (
 `Id` varchar(10) NOT NULL,
 `Name` varchar(255) NOT NULL
 `CompId` varchar(10) NOT NULL,
 `FilId` varchar(10) NOT NULL,
  PRIMARY KEY (`Id`),
  KEY `empl_to_comps` (`VuzId`),
  KEY `empl_to_fils` (`FilId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8


CREATE TABLE `Companies` (
 `Id` varchar(10) NOT NULL DEFAULT '',
 `MainId` varchar(10) DEFAULT '',
 `Type` varchar(255) NOT NULL,
 `Name` varchar(255) NOT NULL
 PRIMARY KEY (`Id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

Answer 1

SELECT DISTINCT e.*
FROM Employees e
JOIN Companies c ON c.Id IN (e.CompId, FilId);

SELECT e.*
FROM Employees e
LEFT JOIN Companies c ON c.Id IN (e.CompId, FilId)
WHERE c.Id IS NULL;

更新

根据数据和索引，以下两个查询可能会更快。虽然冗长，但它们比JOIN查询更具表现力。

SELECT e.*
FROM Employees e
WHERE EXISTS (
        SELECT *
        FROM Companies c
        WHERE c.Id = e.CompId
   )
   OR EXISTS (
        SELECT *
        FROM Companies c
        WHERE c.Id = e.FilId
   );


SELECT e.*
FROM Employees e
WHERE NOT EXISTS (
      SELECT *
      FROM Companies c
      WHERE c.Id = e.CompId
  )
  AND NOT EXISTS (
      SELECT *
      FROM Companies c
      WHERE c.Id = e.FilId
  );

使用2个外键查找不匹配的记录

1 个答案:

更新