On 05/03/2019 01:33, Richard Hipp wrote:
On 3/4/19, Kyle <kmccord0...@gmail.com> wrote:
On another DB I came across 2 stmts, that I think are equivalent, but
generated different explain plans. I request a second opinion - are
these 2 stmts equivalent? If so, why do they generate different explain
plans even on sqlite?
The two SELECT statements below may well compute the same output
(unless I'm missing something) but they are not the same. The WHERE
clause in the subquery is different. So why do you expect them to
generate the same query plan?
create table t1(c,d);
create table t2(c,d);
explain select * from t1
where c=1 and d in (select d from t2 where c=1);
explain select * from t1
where c=1 and d in (select d from t2 where t2.c=t1.c);
DRH, many thanks for your reply, I was expecting same output because I
believe stmts to be equivalent, so was not sure why query plan was
different. I see the explain plans are very similar.
But I believe original stmts mentioned are still equivalent?
Do you agree? And in SQLite what is best way to write such stmt (or in
other terms, what is difference)?
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