if condition in sql server update query

Question

I have a SQL server table in which there are 2 columns that I want to update either of their values according to a flag sent to the stored procedure along with the new value, something like:

UPDATE     table_Name  SET     CASE         WHEN @flag = '1' THEN column_A += @new_value         WHEN @flag = '0' THEN column_B += @new_value     END AS Total  WHERE     ID = @ID 

What is the correct SQL server code to do so??

Answer 1

Something like this should work:

UPDATE     table_Name SET    column_A = CASE WHEN @flag = '1' THEN column_A + @new_value ELSE column_A END,   column_B = CASE WHEN @flag = '0' THEN column_B + @new_value ELSE column_B END WHERE     ID = @ID 

Answer 2

The current answers are fine and should work ok, but what's wrong with the more simple, more obvious, and more maintainable:

IF @flag = 1     UPDATE table_name SET column_A = column_A + @new_value WHERE ID = @ID; ELSE     UPDATE table_name SET column_B = column_B + @new_value WHERE ID = @ID; 

This is much easier to read albeit this is a very simple query.

Here's a working example courtesy of @snyder: SqlFiddle.