Assign row numbers to a set of results retrieved via a PL-SQL Stored Procedure

Question

I have a stored procedure which performs a number of select statements, and joins the results using a UNION , eg

OPEN myItems FOR
   SELECT column1, columns2 ... FROM table1 WHERE myCondition
   UNION
   SELECT column1, column2 ... FROM table2 WHERE myCondition
   UNION
   SELECT column1, column 2....
END

and so on.

I need to be able to uniquely identify the data being returned, and so I was hoping to be able to assign a row number to the rows that are returned.

I imagine there's an easy way to do this, but unfortunately I haven't been able to find it!

Thanks

Answer 1

SELECT ROW_NUMBER() OVER (ORDER BY column1) AS row_num, t.* 
FROM (
   SELECT column1, columns2 ... FROM table1 WHERE myCondition
   UNION
   SELECT column1, column2 ... FROM table2 WHERE myCondition
   UNION
   SELECT column1, column 2.... 
) t;