Question

I’m wondering how others handle this situation… and how to apply the Don’t Repeat Yourself (DRY) principle to this situation.

I find myself constantly PIVOTing or writing CASE statements in T-SQL to present Months as columns. I generally have some fields that will include (1) a date field and (2) a value field. When I present this back to a user through an ASPX page or Reporting Services I need to have the last right-most 14 columns to have this pattern:

[Year],[Jan],[Feb],[Mar],[Apr],[May],[Jun],[Jul],[Aug],[Sep],[Oct],[Nov],[Dec],[Total]

Where year is the year as an int and every other field is the value field summed for that month (except for [Total] which is the total value field for the year).

I’d like to find one re-usable way to handle this. Open to all suggestions (T-SQL / ANSI SQL)

Answer 1

This isn’t exactly what you’re looking for, but I’ve done a lot of repetitive UNPIVOT, and typically, I would code-gen this, with some kind of standardized naming and use CTEs heavily:

WITH P AS (     SELECT Some Data             ,[234] -- These are stats             ,[235]     FROM Whatever      ) ,FINAL_UNPIVOTED AS (     SELECT Some Data             ,[STAT]     FROM P     UNPIVOT (         STAT FOR BASE IN ([234], [235])      ) AS unpvt     WHERE STAT <> 0 ) SELECT Some Data               ,CONVERT(int, FINAL_UNPIVOTED.[BASE]) AS [BASE]               ,FINAL_UNPIVOTED.[STAT] FROM FINAL_UNPIVOTED 

You can codegen by inspecting a table or view and using something like this:

DECLARE @sql_unpivot AS varchar(MAX) SELECT @sql_unpivot = COALESCE(@sql_unpivot + ',', '') + COLUMN_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'whatever' 

And templatizing the code:

SET @template = '     WITH P AS (         SELECT Some Data                 ,{@sql_unpivot}                   FROM Whatever          )     ,FINAL_UNPIVOTED AS (         SELECT Some Data                 ,[STAT]         FROM P         UNPIVOT (             STAT FOR BASE IN ({@sql_unpivot})          ) AS unpvt         WHERE STAT <> 0     )     SELECT Some Data                   ,CONVERT(int, FINAL_UNPIVOTED.[BASE]) AS [BASE]                   ,FINAL_UNPIVOTED.[STAT]     FROM FINAL_UNPIVOTED ' SET @sql = REPLACE(@template, '{@sql_unpivot}', @sql_unpivot) 

etc.

Of course, it’s possible to run this code dynamically or create and SP and you can swap out a view or table you created temporarily just to pick up metadata for something inline.

See comments regarding table-valued functions and OUTER APPLY technique.