Question

我有一个典型的问题。

我需要修改以下T SQL查询。目前它只在一个表中查找信息。我需要查看两个具有相同列的表格以供参考。一个表包含当前员工，一个包含前员工

SELECT t.net_Id
      ,e.fname
      ,e.lname
FROM tblTrackingEmployee t
    join view_employee e 
        on e.net_id = t.net_id
where trackingid = @trackingId
and empType = @empType

我在想的是使用联盟来查看两者。员工将出现在一个表或另一个表中，它将永远不会出现在两个表中。

SELECT t.net_Id
      ,e.fname
      ,e.lname
FROM tblTrackingEmployee t
    JOIN view_employee e
        ON e.net_id = t.net_id
WHERE trackingid = @trackingId
AND empType = @empType
union 
SELECT t.net_Id
      ,fe.fname
      ,fe.lname
FROM tblTrackingEmployee t
      JOIN view_employee fe 
             ON fe.net_id = t.net_id
WHERE trackingid = @trackingId
AND empType = @empType

然而，这是扭曲，我需要知道返回的人是现任或前任雇员。有没有办法在返回的表中添加一个列，如果是当前员工，则为1;如果是前员工，则为0？每个trackingId都可能包含两种类型的员工。

Answer 1

为每个SELECT子句添加一个常量列 - 您可以使用别名：

SELECT t.net_Id
      ,e.fname
      ,e.lname
      ,'Current' AS Type
FROM tblTrackingEmployee t
    JOIN view_employee e
        ON e.net_id = t.net_id
WHERE trackingid = @trackingId
AND empType = @empType
union 
SELECT t.net_Id
      ,fe.fname
      ,fe.lname
      ,'Former'
FROM tblTrackingEmployee t
      JOIN view_formerEmployee fe 
             ON fe.net_id = t.net_id
WHERE trackingid = @trackingId
AND empType = @empType

Answer 2

让我直截了当地说，你有两张桌子，一张是现任员工，一个是前雇员？这是一个坏主意，你可能已经有一个状态表（'活动'/'无效'）。在任何情况下，只需添加一个字段，如int，您想要每个查询

SELECT
 0 AS TheField,
  ....
FROM
  Table
UNION ALL
SELECT
1 AS TheField,
 ...
FROM
  table

Answer 3

如果您愿意，也可以按状态排序：

 SELECT U.* FROM
 (
  SELECT t.net_Id AS ID
      ,e.fname AS FName
      ,e.lname AS LName
      ,'Current' AS EmployStatus
  FROM tblTrackingEmployee t
      JOIN view_employee e
          ON e.net_id = t.net_id
  WHERE trackingid = @trackingId
  AND empType = @empType
  union 
  SELECT t.net_Id AS ID
      ,fe.fname AS FName
      ,fe.lname AS LName
      ,'Former' AS EmployStatus
  FROM tblTrackingEmployee t
        JOIN view_formerEmployee fe
               ON fe.net_id = t.net_id
  WHERE trackingid = @trackingId
    AND empType = @empType
) AS U
 ORDER BY U.EmployStatus

识别从中检索的表数据

3 个答案: