Maarten Fokkinga (fokkinga@cs.utwente.nl) reports a bug with a severity of 2
The lower the number the more severe it is.
Short Description
Three levels deeply nested SELECT goes wrong
Long Description
A 3 levels deeply nested SELECT with "R(a)" in the top-most FROM part and "R.a=S.a AND XXX" in the middle WHERE part
maygive different results if in a SELECT within XXX the term "S.a" is replaced by "R.a".
Since the innermost SELECT lies in the "scope" of the conjunct "R.a=S.a", it should not make any difference if "R.a" is
usedor "S.a".
See the simple example code to reproduce the error.
Version: PostgreSQL 7.0.3 on i686-pc-linux-gnu, compiled by gcc 2.96
Sample Code
create table R(a int);
create table S(a int, b int);
create table T(a int, b int);
insert into R values (1);
insert into R values (2);
insert into S values (2,20);
insert into S values (1,10);
insert into T values (2,20);
insert into T values (1,10);
-- the order of the rows in R, S, T is significant
-- first query:
select a from R where
exists (select b from S where
S.a=R.a AND S.b in (select b from T where a=S.a));
-- gives two rows (rows "(1)" and "(2)")
-- second query:
select a from R where
exists (select b from S where
S.a=R.a AND S.b in (select b from T where a=R.a));
-- gives one row ("(1)" only)
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