用于确定表中是否存在的SQL查询 [英] SQL query for determining presence in table

问题描述

我有一个学生ID和我的数据库中的多个表为学生的信息，给予任何id，它只存在一个表。每个表都有属性学生id。

I have a student id and multiple tables in my database all for info of students such that given any id, it is present only in one table. Each table has attribute Student id.

给定学生id，如何使用SQL查询确定表有学生的信息与该学生id？

Given a student id, how to use SQL query to determine table has the info of student with that student id?

推荐答案

   IF EXISTS(SELECT TOP 1 1 FROM table WHERE studentID = @input)
   BEGIN
      -- do stuff
   END

b
$ b

or slightly less fancy

   IF EXISTS(SELECT TOP 1 studentID FROM table WHERE studentID = @input)
   BEGIN
      -- do stuff
   END

您还可以创建查询视图/查询。像这样：

you could also make a lookup view / query. something like this:

   SELECT sudentID, 'Table1' as Location
   FROM 'Table1'
   UNION ALL
   SELECT sudentID, 'Table2' as Location
   FROM 'Table2'
   UNION ALL
   SELECT sudentID, 'Table3' as Location
   FROM 'Table3'
   UNION ALL
   SELECT sudentID, 'Table4' as Location
   FROM 'Table4'

然后查询此视图的位置。如果您需要加入

Then query this view for location. This can be useful if you need to joins

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