MS Sql: Conditional ORDER BY ASC/DESC Question

Question

I want to to make to make the ordering in my query conditional so if it satisfiess the condition it should be ordered by descending

For instance:

SELECT * FROM Data ORDER BY SortOrder CASE WHEN @Direction = 1 THEN DESC END

Answer 1

I have done something like this

select productId, InventoryCount, 
    case 
    when @Direction = 1 then InventoryCount 
    else -InventoryCount 
    end as "SortOrder"
order by 3

Answer 2

Don't change the ASC or DESC, change the sign of the thing being sorted-by:

SELECT * FROM table 
ORDER BY 
CASE WHEN @Direction = 1 THEN -id else id END asc;

The OP asks:

Guys, I am not the SQL Expert, please explain me what means the id and -id, does it controls the ordering direction?

id is just whatever column you're sorting by; -id is just the negation of that, id * -1. If you're sorting by more than one column, you'll need to negate each column:

SELECT * FROM table 
ORDER BY 
CASE WHEN @Direction = 1 THEN -id else id END 
CASE WHEN @Direction = 1 THEN -othercolumn else othercolumn END ;

If you're ordering by a non numeric column, you'll need to find an expression that makes that column "negative"; writing a function to do that may help.

Answer 3

SELECT * 
FROM Data 
ORDER BY 
Case WHEN @Direction = 1 THEN SortOrder END DESC, 
Case WHEN 1=1 THEN SortOrder END