Question

Ok, I have a table that has 10 years worth of data, and performance is taking a hit. I am planning on moving the older data to a seperate historicaltable. the problem is i need to select from the first table if it is in there and the 2nd table if not. I do not want to do a join because then it will do a lookup on the 2nd table always. HELP?

Answer 1

IF you still need to query the data in no way would I move it to another table. How big is the table now? What are the indexes? Have you considered partioning the table?

If you must move to another table, you could query in stored procs with an if statement. Query the main table first and then if the rowcount = 0 query the other table. It will be slower for records not in the main table but should stay fast if they are in there. However, it wouldn’t know when you need records from both.

Sample of code to do this:

CREATE PROC myproc (@test INT)
AS
SELECT field1, field2 from table1field1, field2 from table1
 IF @@rowcount = 0
 BEGIN
 SELECT field1, field2 FROM table2 field1, field2 from table1
 END

But really the partioning and indexing correctly is probaly your best choice. Also optimize existing queries. If you are using known poorly performing techniques such as cursors, correlated subqueries, views that call views, scalar functions, nonsargable where clauses, etc. just fixing your queries may mean you don’t have to archive.

Sometimes, buying a better server would help as well.