Question

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.

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

Answer 1

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

or slightly less fancy

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

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'

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