Getting an error when executing a dynamic sql within a function (SQL Server)?

Question

I create a function to execute dynamic SQL and return a value. I am getting "Only functions and some extended stored procedures can be executed from within a function." as an error.

The function:

Create Function fn_GetPrePopValue(@paramterValue nvarchar(100))
returns int as
begin
declare @value nvarchar(500);

Set @SQLString  = 'Select Grant_Nr From Grant_Master where grant_id=' + @paramterValue

exec   sp_executesql
       @query = @SQLString,       
       @value = @value output

return @value   
end

The execution:

Select dbo.fn_GetPrePopValue('10002618') from Questions Where QuestionID=114

and:

Select fn_GetPrePopValue('10002618') from Questions Where QuestionID=114

Is the function being called properly or is the function incorrect?

Aleksandr Fedorenko · Accepted Answer · 2013-03-02T23:35:31.687

9

You cannot use dynamic SQL from a function, neither can you call stored procedures.

Create proc GetPrePopValue(@paramterValue nvarchar(100))
as
begin
declare @value nvarchar(500),
        @SQLString nvarchar(4000)

Set @SQLString = 'Select @value = Grant_Nr From Grant_Master where grant_id = @paramterValue'

exec sp_executesql @SQLString, N'@paramterValue nvarchar(100)', 
       @paramterValue, 
       @value = @value output

return @value   
end

edited Mar 02 '13 at 23:35

answered Mar 02 '13 at 23:28

Aleksandr Fedorenko

16,594
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BTW, for preventing SQL Injection use sp_executesql with parameters – Aleksandr Fedorenko Mar 02 '13 at 23:37
This approach won't work if the OP's function is being used by a Check Constraint - they can't (AFAIK) use stored procedures. – radders Jun 03 '19 at 13:36

score 2 · Answer 2 · answered Mar 02 '13 at 23:35

Functions are limited in what they can use, so that you can use them in a query without accidentally make something that would give horrible performance. Using dynamic queries is one of those things, as that would cause a query planning for each execution, and also would keep the function from being able to be part of a query plan.

You don't need the dynamic query at all in this case, just return the value:

Create Function fn_GetPrePopValue(@paramterValue nvarchar(100))
returns int as
begin

return (select Grant_Nr From Grant_Master where grant_id = @paramterValue)

end

score 0 · Answer 3 · answered Mar 02 '13 at 23:31

I don't think you can use dynamic SQL from a function, nor do I think you need to in your case. Looks like you want something closer to this:

Create Function dbo.fn_GetPrePopValue(@paramterValue nvarchar(100))
returns int as
begin
  declare @value int
  declare @SQLString varchar(MAX)

  Select @value=Grant_Nr From Grant_Master where grant_id=@paramterValue

  return @value
end

SQL Fiddle Demo

Also, please check your data types to make sure you're fields are correct. Seems odd to pass in a varchar for the id and return an int for the other field. Either way, this should help you get going in the right direction.

Getting an error when executing a dynamic sql within a function (SQL Server)?

3 Answers3

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