CREATE MyProc
AS
BEGIN TRY
... write the query
END TRY
BEGIN CATCH
    ...more error handling as necessary
     RETURN ERROR_NUMBER();
END CATCH
RETURN 0;

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

sqlstring = "SELECT ... WHERE 1=1"
if (opt1) then sqlstring = sqlstring + " AND (...)"
if (opt2) then sqlstring = sqlstring + " AND (...)"
if (op33) then sqlstring = sqlstring + " AND (...)"