Hi
what is faster query ?
select Name from Worker
or
select TOP(1) Name from Worker
I have 1,000,000 records
thank's in advance
views:
218answers:
1
+8
A:
If you don't have an ORDER BY or a DISTINCT, SELECT TOP(1) Name FROM Worker is faster.
The reason for this is that if you do happen to have an ORDER BY or a DISTINCT, the query has to go through the entire table to sort and filter out unwanted results. If it's a straight SELECT TOP, however, it can go to the first page, take the first row, and be done with it very quickly.
Eric
2009-06-12 15:24:07
True. Of course if you have 1,000,000 records then selecting top 1 will be faster no matter what. An order by clause will just slow things down further and narrow the difference in speed a bit.
Steve Wortham
2009-06-12 15:31:31
thank's alot !!
Gold
2009-06-12 16:21:48
During execution the query might flow control because the client is unable to parse the result fast enough (consume the 1 mil. names result set). So even with ordering the TOP 1 *may* be faster, depending on how slow the client processing is.
Remus Rusanu
2009-06-12 17:31:01