DESCENDING/ASCENDING Parameter to a stored procedure - tsql

Question

I have the following SP
CREATE PROCEDURE GetAllHouses
set #webRegionID = 2
set #sortBy = 'case_no'
set #sortDirection = 'ASC'
AS
BEGIN
Select
tbl_houses.*
from tbl_houses
where
postal in (select zipcode from crm_zipcodes where web_region_id = #webRegionID)
ORDER BY
CASE UPPER(#sortBy)
when 'CASE_NO' then case_no
when 'AREA' then area
when 'FURNISHED' then furnished
when 'TYPE' then [type]
when 'SQUAREFEETS' then squarefeets
when 'BEDROOMS' then bedrooms
when 'LIVINGROOMS' then livingrooms
when 'BATHROOMS' then bathrooms
when 'LEASE_FROM' then lease_from
when 'RENT' then rent
else case_no
END
END
GO
Now everything in that SP works but I want to be able to choose whether I want to sort ASCENDING or DESCENDING.
I really can't fint no solution for that using SQL and can't find anything in google.
As you can see I have the parameter sortDirection and I have tried using it in multiple ways but always with errors... Tried Case Statements, IF statements and so on but it is complicated by the fact that I want to insert a keyword.
Help will be very much appriciated, I have tried must of the things that comes into mind but haven't been able to get it right.

Answer 1

You could use two order by fields:
CASE #sortDir WHEN 'ASC' THEN
CASE UPPER(#sortBy)
...
END
END ASC,
CASE #sortDir WHEN 'DESC' THEN
CASE UPPER(#sortBy)
...
END
END DESC
A CASE will evaluate as NULL if none of the WHEN clauses match, so that causes one of the two fields to evaluate to NULL for every row (not affecting the sort order) and the other has the appropriate direction.
One drawback, though, is that you'd need to duplicate your #sortBy CASE statement. You could achieve the same thing using dynamic SQL with sp_executesql and writing a 'ASC' or 'DESC' literal depending on the parameter.

Answer 2

That code is going to get very unmanageable very quickly as you'll need to double nest your CASE WHEN's... one set for the Column to order by, and nested set for whethers it's ASC or DESC
Might be better to consider using Dynamic SQL here...
DECLARE #sql nvarchar(max)
SET #sql = '
Select
tbl_houses.*
from tbl_houses
where
postal in (select zipcode from crm_zipcodes where web_region_id = ' + #webRegionID + ') ORDER BY '
SET #sql = #sql + ' ' + #sortBy + ' ' + #sortDirection
EXEC (#sql)

Answer 3

You could do it with some dynamic SQL and calling it with an EXEC. Beware SQL injection though if the user has any control over the parameters.
CREATE PROCEDURE GetAllHouses
set #webRegionID = 2
set #sortBy = 'case_no'
set #sortDirection = 'ASC'
AS
BEGIN
DECLARE #dynamicSQL NVARCHAR(MAX)
SET #dynamicSQL =
'
SELECT
tbl_houses.*
FROM
tbl_houses
WHERE
postal
IN
(
SELECT
zipcode
FROM
crm_zipcodes
WHERE
web_region_id = ' + CONVERT(nvarchar(10), #webRegionID) + '
)
ORDER BY
' + #sortBy + ' ' + #sortDirection
EXEC(#dynamicSQL)
END
GO