SQL User Defined Function Within Select

66
votes

I have a user defined function in SQL called getBuisnessDays it takes @startdate and @enddate and returns the number of business days between the two dates. How can I call that function within my select?

Here's what I'd like to do.. 

SELECT getBusinessDays(a.opendate,a.closedate) 
FROM account a
WHERE ...
3
sqlsql-serverselectuser-defined-functions
Just remember that UDFs can often kill query performance depending on how the optimizer reacts to them. They often mean processing row by row rather than set-based. For your situation you might be better off using a calendar table and selecting against that when needed. - Tom H

3 Answers

108
votes

Yes, you can do almost that: 

SELECT dbo.GetBusinessDays(a.opendate,a.closedate) as BusinessDays
FROM account a
WHERE...
12
votes

If it's a table-value function (returns a table set) you simply join it as a Table

this function generates one column table with all the values from passed comma-separated list

SELECT * FROM dbo.udf_generate_inlist_to_table('1,2,3,4')
8
votes

Use a scalar-valued UDF, not a table-value one, then you can use it in a SELECT as you want.