SQL Function for SumIf 2012 [duplicate] - sql

Question

This question already has an answer here:
Creating SumIf function in SQL Server 2012
(1 answer)
Closed 7 years ago.
I have the following sql function, but not running correctly, the intended returned value is the total
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
Create FUNCTION [dbo].[SumIf](#ColumnName [varchar](100), #Criteria [varchar](500))
RETURNS [decimal] AS
BEGIN
-- Declare the return variable here
DECLARE #Total Decimal
DECLARE #TableName Decimal
Select #Total = SUM(#ColumnName) from #TableName where #Criteria
RETURN #Total
END
the use syntax would be something like
Select dbo.sumif(fees.fee_amount, Fees.Fee_Code ='B01')
So the tablename would also need to be extracted from the columnname variable passed.

Answer 1

I don't think you will be able to implement your function that way. You're essentially trying to pass an expression to the function which I don't think is possible in SQL Server. You may be able to do it with dynamic SQL passing in strings but not as cleanly as you're hoping.

Answer 2

you need dynamic SQL to do this, but unfortunately you can't use dynamic SQL inside a UDF. try this-
DECLARE #ColumnName [nvarchar](100) = '' --fill in values here
DECLARE #TableName [nvarchar](100) = ''
DECLARE #Criteria [nvarchar](500) = ''
DECLARE #s nvarchar(max)
DECLARE #res bigint
set #s = 'SELECT #result = SUM(' + #ColumnName + ') from ' + #TableName + ' where ' + #Criteria
exec sp_executesql #s, N'#result OUTPUT', #result = #res OUTPUT
select #res

Answer 3

You are way on the wrong track. If you wanted to put sumif() in a select statement, it would need to be a user-defined aggregation function, rather than just a user-defined function. The fact that you've declared #TableName to be decimal and then use it in a from clause points to other issues.
So, my suggestion is that you just do this in-line:
select sum(case when <condition> then <columnname> else 0 end) as sumval
from <tablename>
If you wanted a programming block to put the data together, then use a stored procedure. Something like:
Create FUNCTION [dbo].SumIf(#ColumnName varchar(100),
#TableName varchar(255)
#Criteria varchar(500),
#Total Decimal OUTPUT)
) AS
BEGIN
DECLARE #sql nvarchar(max) = 'Select #Total = SUM(#ColumnName) from #TableName where #Criteria';
set #sql = replace(#sql, '#ColumnName', #ColumnName);
set #sql = replace(#sql, '#TableName', #TableName);
set #sql = replace(#sql, '#Criteria', #Criteria);
sp_execute_sql #sql, N'#total decimal output', #total = #total output;
END;