MS Sql: Conditional ORDER BY ASC/DESC 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

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.