Question

I have a program that must support both Oracle and SQL Server for it’s database.
At some point I must execute a query where I want to concatenate 2 columns in the select statement.

In SQL Server, this is done with the + operator

select column1 + ' - ' + column2 from mytable

And oracle this is done with concat

select concat(concat(column1, ' - '), column2) from mytable

I’m looking for a way to leverage them both, so my code has a single SQL query literal string for both databases and I can avoid ugly constructs where I need to check which DBMS I’m connected to.

My first instinct was to encapsulate the different queries into a stored procedure, so each DBMS can have their own implementation of the query, but I was unable to create the procedure in Oracle that returns the record set in the same way as SQL Server does.

Update: Creating a concat function in SQL Server doesn’t make the query compatible with Oracle because SQL Server requires the owner to be specified when calling the function as:

select dbo.concat(dbo.concat(column1), ' - '), column2) from mytable

It took me a while to figure it out after creating my own concat function in SQL Server.

On the other hand, looks like a function in Oracle with SYS_REFCURSOR can’t be called with a simple

exec myfunction

And return the table as in SQL Server.

In the end, the solution was to create a view with the same name on both RDBMs but with different implementations, then I can do a simple select on the view.

Answer 1

If you want to go down the path of creating a stored procedure, whatever framework you’re using should be able to more or less transparently handle an Oracle stored procedure with an OUT parameter that is a SYS_REFCURSOR and call that as you would a SQL Server stored procedure that just does a SELECT statement.

CREATE OR REPLACE PROCEDURE some_procedure( p_rc OUT sys_refcursor )
AS
BEGIN
  -- You could use the CONCAT function rather than Oracle's string concatenation
  -- operator || but I would prefer the double pipes.
  OPEN p_rc
   FOR SELECT column1 || ' - ' || column2
         FROM myTable;
END;

Alternatively, you could define your own CONCAT function in SQL Server.