Question

伙计我在SQL数据库中有三个表。 tblTicketDetail，tblEngineer和tblTicket_Engineer（多对多关系的联结表）。在我的应用程序中发生的情况是，当我生成新票证时，票证被分配给一个，两个或三个（最大）工程师（因此是多对多关系）。

以下是表格的结构：

tblTicketDetail

+----------+---------------+--------+ | TicketID | Desc | Status | +----------+---------------+--------+ | 1 | Description 1 | 1 | | 2 | Description 2 | 0 | | 3 | Description 3 | 1 | +----------+---------------+--------+

tblEngineer

+------------+-------+ | EngineerID | Name | +------------+-------+ | 1 | Tom | | 2 | Harry | | 3 | John | +------------+-------+

tblTicket_Engineer

+----------+------------+ | TicketID | EngineerID | +----------+------------+ | 1 | 1 | | 1 | 2 | | 1 | 3 | | 2 | 1 | | 3 | 1 | | 3 | 2 | +----------+------------+

现在我要做的是COUNT所有TicketID的{{1}}为status，EngineerID应该是特定的（例如1）。我尝试了这个查询，但它生成两个计数

SELECT  (
          SELECT COUNT(*) total
          FROM   tblTicketDetail WHERE Status = 1
        ) AS count1,
        (
          SELECT COUNT(*) total
          FROM   tblTicket_Engineer WHERE EngineerID = 1
        ) AS count2

在这种情况下（其中EngineerID = 1），查询应该生成2的计数。我应该怎么做呢？

Answer 1

您需要在子查询上创建联接以获取故障单状态，子查询应如下所示：

      SELECT COUNT(*) total
      FROM   tblTicket_Engineer
      INNER JOIN  tblTicketDetail ON tblTicketDetail.TicketID = tblTicket_Engineer.TicketID AND tblTicketDetail.Status = 1
      WHERE tblTicket_Engineer.EngineerID = 1

Answer 2

我认为以下代码可以帮助您

SELECT Count(*) FROM 
tblTicket inner join tblTicket_Engineer on 
(tblTicket.TicketID= tblTicket_Engineer.TicketID)
WHERE  tblTicket.Status = '1' 
AND tblTicket_Engineer.EngineerID = '1'

Answer 3

你可以试试这个查询

SELECT COUNT(tblTicketDetail.TicketID) FROM tblTicketDetail 
JOIN tblTicket_Engineer ON  tblTicket_Engineer.TicketID = tblTicketDetail.TicketID    
WHERE tblTicket_Engineer.EngineerID = 1
AND tblTicketDetail.Status = 1

Answer 4

你可以这样做

SELECT COUNT(*) total
FROM   tblTicketDetail a, tblTicket_Engineer b
WHERE  a.TicketID = b.TicketID AND a.Status = 1 AND b.EngineerID = 1

Answer 5

试试这个，这可能会对你有所帮助。

SELECT COUNT(*) total 
FROM tblTicketDetail as td, tblTicket_Engineer as te 
WHERE td.Status = 1 
      AND te.EngineerID = 1;

Answer 6

您可能想要使用JOIN：

  SELECT COUNT(*) total
  FROM   tblTicket NATURAL JOIN tblTicket_Engineer NATURAL JOIN tblEngineer
  WHERE  Status = 1 AND EngineerID = 1

如果您的数据库引擎不支持多个NATURAL JOIN子句，或者您不想使用它们，您可以采用明确的JOIN

  SELECT COUNT(*) total
  FROM   tblTicket INNER JOIN tblTicket_Engineer ON (TicketID)
         INNER JOIN tblEngineer ON (EngineedID)
  WHERE  Status = 1 AND EngineerID = 1

注意不要在生产环境中使用NATURAL JOIN 。请参阅this post。

如何在带有WHERE子句的两个表上使用COUNT

6 个答案: