Question

Running SQL Server 2005. A piece of software integrates with our database. Unfortunately they chose to make direct SQL queries instead of using stored procedures. Now we have changed our database scheme and the query in question is no longer valid.

Is it possible to patch T-SQL in runtime, on SQL Server?

E.g.
When SQL Server gets a SELECT A FROM InvalidTable for a specific database, the query would be converted to SELECT A FROM ValidTable just before it gets executed.

Edit:
This is the query in question:

SELECT * FROM DataTable c JOIN Users u ON u.UserName = @P0 AND c.DepartmentID = b2.DepartmentID WHERE c.Status = 0 where DepartmentID has moved to another table!

Answer 1

You can use Views and Synonyms to hide schema changes.

So for simple things (like InvalidTable is now ValidTable), you can define a synonym

CREATE SYNONYM InvalidTable FOR CorrectSchema.ValidTable;

For more complex things (columns, JOINs, table splits, data types etc) you need a view

CREATE VIEW InvalidTable 
AS
SELECT 
   col1, col2, 
   CAST(col3 AS varchar(1000)) AS col3, -- fix data type
   1 AS col4  -- not used now, but expected in legacy calls
FROM
   CorrectSchema.ValidTable
WHERE
   col5 = 'Something'
GO

Edit, after OP realises they’ve bollixed themselves

You can’t have a view or synonym if a table exists with the same name in the same database.

So, use another DB and make the legacy app use that instead. In the examples, you’d have DataTable in another db with the assumption you can use another DB withoout changing code

USE legacyDB
GO
CREATE VIEW DataTable
AS
SELECT
   *
FROM
   CorrectDB.CorrectSchema.ValidTable V
   JOIN
   CorrectDB.CorrectSchema.OtherTable O ON ...
GO

Otherwise, rename the correct DB and point all non-legacy code to the renamed DB.