SQL Efficiency: WHERE IN Subquery vs. JOIN then GROUP

Question

As an example, I want to get the list of all items with certain tags applied to them. I could do either of the following:

SELECT Item.ID, Item.Name
FROM Item
WH         


        

Answer 1

SELECT Item.ID, Item.Name
...
GROUP BY Item.ID

This is not valid T-SQL. Item.Name must appear in the group by clause or within an aggregate function, such as SUM or MAX.