Top 1 faster if only selecting one row

Does the database break the selection loop as fast as it has got one record when using Top 1?

So that select top 1 * from customer where cusId = 1234

is faster than select * from cust开发者_如何学Comer where cusId = 1234 ?

cusId is unique, so does MSSql understand to do it "faster" without top 1?

If cusId is a primary key, both should be the same re: performance.

EDIT:

You are only adding overhead with TOP 1 if you have unique index that will return 1 result anyway.

It will be different if you have order by something than you are interested in only one row.

MORE:

There is no looping involved, unless there is a table scan involved and there is no index at all for cusId. In that case, TOP 1 can't help you anyway.

In my opinion select * from customer where cusId = 1234 will be more faster..b/c it has one operation less to perform than first one...