Executing dynamic SQL in a SQLServer 2005 function

Question

I will preface this question by saying, I do not think it is solvable. I also have a workaround, I can create a stored procedure with an OUTPUT to accomplish this, it is jus

Answer 1

Here is the solution

Solution 1: Return the dynamic string from Function then

Declare @SQLStr varchar(max) 
DECLARE @tmptable table (<columns>)
set @SQLStr=dbo.function(<parameters>)
insert into @tmptable
Exec (@SQLStr)

select * from @tmptable

Solution 2: call nested functions by passing parameters.

Answer 2

Thank you all for the replies.

Ron: FYI, Using that will throw an error.

I agree that not doing what I originally intended is the best solution, I decided to go a different route. My two choices were to use sum(cast(BINARY_CHECKSUM(*) as float)) or an output parameter in a stored procedure. After unit testing speed of each, I decided to go with sum(cast(BINARY_CHECKSUM(*) as float)) to get a comparable checksum value for each table's data.

Answer 3

Because functions have to play nicely with the query optimiser there are quite a few restrictions on them. This link refers to an article that discusses the limitations of UDF's in depth.

Answer 4

It "ordinarily" can't be done as SQL Server treats functions as deterministic, which means that for a given set of inputs, it should always return the same outputs. A stored procedure or dynamic sql can be non-deterministic because it can change external state, such as a table, which is relied on.

Given that in SQL server functions are always deterministic, it would be a bad idea from a future maintenance perspective to attempt to circumvent this as it could cause fairly major confusion for anyone who has to support the code in future.

Answer 5

You can get around this by calling an extended stored procedure, with all the attendant hassle and security problems.

http://decipherinfosys.wordpress.com/2008/07/16/udf-limitations-in-sql-server/

http://decipherinfosys.wordpress.com/2007/02/27/using-getdate-in-a-udf/