Simple query ... syntax error ?

Question

What is wrong with this simple sql statement ?
SELECT Caseid
FROM (SELECT DISTINCT Caseid, userid FROM Atts)
I get this error
Server: Msg 170, Level 15, State 1, Line 2
Line 2: Incorrect syntax near ')'.

Answer 1

In this case, it could go either way. Because the derived
table is
performing the select distinct anyway, the execution plans
would be similar,
but you'd see one extra step for selecting all rows from the
derived table.
Notice that the derived table has distinct caseid, userid,
but the main
query only selects caseid. If the extra IO required to
transmit the
unwanted userid column is more expensive than the extra step
required to
select just the caseid column out of the derived table, then
the derived
table is the better choice.
In any case, the simpler query is usually the better option.
Unless he
actually wants a duplicate caseid for each userid, but not
the userid
itself, plain ol' SELECT DISTINCT makes more sense.
"bregent" <[email protected]> wrote in
message
news:ejaad1$k2u$[email protected]..
> >On the contrary, subqueries in the FROM clause are
quite useful and can
> >in
> >the right situations perform much better than
alternative queries.
>
> Ah, as usual you are correct. It looks like he forgot to
add a DT alias
> name
> at the end of the statement which is causing the error.
But in any case, a
> simple select distinct would yield the same results and
performance,
> correct?
>