Question

I have a stored procedure to return the top 50 rows from a table, like this:

select top 50 
    Puzzle, 
    min(DateSolved) as CreationDate, 
    avg(SecondsToComplete) as AverageTime, 
    count(*) as TimesSolved 
  from CustomSolves
  group by Puzzle

But I want the stored procedure to accept two parameters, so that I can order by a custom column (the creation date, the average time, or the times sovled) and only select records newer than a certain date. Something like this pseudo-SQL:

procedure SelectCustomPuzzles
  @CutoffDate datetime,
  @SortColumn column
as
  select top 50 
      Puzzle, 
      min(DateSolved) as CreationDate, 
      avg(SecondsToComplete) as AverageTime, 
      count(*) as TimesSolved 
    from CustomSolves
    where CreationDate > @CutOffDate
    group by Puzzle
    order by @SortColumn

How could I go about doing something like this?

Answer 1

order by 
   CASE @SortColumn WHEN 'foo ASC' THEN foo ELSE NULL END,
   CASE @SortColumn WHEN 'foo DESC' THEN foo ELSE NULL END DESC,
   CASE @SortColumn WHEN 'bar ASC' THEN bar ELSE NULL END,
   CASE @SortColumn WHEN 'bar DESC' THEN bar ELSE NULL END DESC,

Edit, for a default sort add one of these

...
CASE  WHEN @SortColumn IS NULL THEN default ELSE NULL END DESC

...
defautcolumn

Notes:

• ASC or DESC can’t be in the CASE: has to be outside
• A single CASE with multiple WHEN..THEN column requires datatypes to be implicitly CASTable. I prefer separate CASE expressions to avoid implicit conversions See https://dba.stackexchange.com/a/4166/630 for a worked example