Question

I need to create a view, however the data is generated from an application with its own db management for tables which based on column count can create over 7 SQL Server tables for one internal table definition.

The tables all end with [‘m’ & number], eg devicem1, devicem2 … devicem10

They all contain logical_name as their primary key, but you can never rely on which table will hold any other column in the internal table!

I need to create a view that joins the tables together as just device so when the application changes it doesn’t mess up any stored procs I want to create.

Based on this query:

CREATE VIEW device AS
   SELECT *
   FROM devicem1 m1, devicem2 m2, devicem3 m3, ... devicem10 m10
   WHERE m1.logical_name = m2.logical_name
   AND m1.logical_name = m3.logical_name
   ...
   AND m1.logical_name = m10.logical_name

Is there some way to join ten tables where I can ignore the fact that devicem9 & devicem10 may not exist?

Answer 1

With regards to the requirements of a view. The tables referenced MUST exist when the view is created. The SQL engine isn’t going to allow you to create a view referencing tables that don’t exist.

Considering that a view is just a stored select statement, after it’s created the tables can be deleted (as long as schema-binding isn’t in play); however any time you call or use the view all referenced tables must exist or it will toss an error.

Also, you CAN change the schema of referenced tables as long as it doesn’t remove any fields specifically used in the view but again, if a specific column used by the view is missing any query using the view will fail.

You might have more luck getting away with what your trying to do with some creative table valued functions and dynamic sql. A table valued function is basically just a view that allows parameters and extended logic.

All in all, I would say what your describing sounds a little sketchy though.