It's hard to compose a topic name for me. But I can show an example :
WHERE (SELECT [ID_Line] FROM [Event] WHERE [Event].[Name] = [A].[Col]) = 2
AND (SELECT [DataType] FROM [Event] WHERE [Event].[Name] = [A].[Col]) = 2
Here I'm processing 2 queries when I really need something like that :
WHERE (SELECT [ID_Line],[DataType] FROM [Event] WHERE [Event].[Name] = [A].[Col]) = 2,2
but SQL doesn't work with tuples, so must I make Inner Join here ?