Question

我有一个worker表和一个关联的workerGeofence表。

CREATE TABLE IF NOT EXISTS `workergeofences` (
`ID` int(11) NOT NULL,
  `WorkerID` varchar(20) NOT NULL,
  `GeofenceID` int(11) NOT NULL,
  `isActive` tinyint(4) NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=107 DEFAULT CHARSET=latin1;

我只需要返回在workerGeofences表中至少有一个条目且isActive为1的工人。

我能够通过以下方式获得理想的结果：

    SELECT distinct w.ID, Title, FName, SName, Email, Birthday, Address, Phone, description,
 companyID 
FROM Workers w WHERE companyID = ? 
and w.ID IN (SELECT WorkerID FROM WorkerGeofences WHERE isActive <> 0)
    limit ?,10

但是子查询是详尽无遗的，因为当我运行解释时，我可以看到它正在扫描整个表格。我该如何解决这个问题？

Answer 1

您走在正确的轨道上，但您不需要select distinct。这会减慢查询速度，除非您知道存在重复项 - 但这不太可能，因为您选择的是WOrkers.Id。

SELECT w.* 
FROM Workers w 
WHERE w.companyID = ? AND
      EXISTS (SELECT 1
              FROM workerGeofences wg
              WHERE w.ID = wg.WorkerID AND wg.isActive <> 0
             )
LIMIT ?, 10;

然后，对于此查询，您需要Workers(CompanyId, Id)和workerGeofences(WorkerId, isActive)上的索引。

注意：为方便起见，我只是放入select *。我假设所有列都来自Workers表。

Answer 2

首先，你的加入是错误的！你没有比较两个表上的任何常见列，你应该添加workerGeofences.workerID = w.id这样的地方：

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第二，你没有从第二张表中选择任何东西，所以加入是unessesary，在你的IN语句中，你没有比较正确的ID，所以你的查询应该是：

SELECT  w.ID, Title, FName, SName, Email, Birthday, Address, Phone,
        description, companyID
    FROM  Workers w
    join  workerGeofences
    WHERE  workerGeofences.workerID = w.ID companyID = ?
      and  w.ID IN (
        SELECT  WorkerID
            FROM  WorkerGeofences s
            WHERE  isActive <> 0
              and  s.workerID = w.id
                   )
    limit  0,10

此外，您可以使用EXISTS（）。

SELECT  w.ID, Title, FName, SName, Email, Birthday, Address, Phone,
        description, companyID
    FROM  Workers w
    WHERE  companyID = ?
      and  w.ID IN (
        SELECT  WorkerID
            FROM  WorkerGeofences s
            WHERE  isActive <> 0
              and  s.workerID = w.ID
                   )
    limit  0,10

Answer 3

使用JOIN完整性：

SELECT DISTINCT w.ID,
       w.Title, 
       w.FName, 
       w.SName, 
       w.Email, 
       w.Birthday, 
       w.Address, 
       w.Phone, 
       w.description, 
       w.companyID
  FROM Workers w 
  JOIN WorkerGeofences wg
    ON wg.workerID = w.id
   AND wg.isActive = 1
 WHERE w.companyID = ? 
 LIMIT ?,10

优化IN子查询

3 个答案: