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https://issues.apache.org/jira/browse/DERBY-6563?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13989500#comment-13989500
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Knut Anders Hatlen commented on DERBY-6563:
-------------------------------------------
It also affects NULLIF, since ConditionalNode is used by both CASE and NULLIF.
For example, these two queries are equivalent, but they return different
results:
{noformat}
ij> select * from (values false) v(b) where not(nullif(b, true));
B
-----
0 rows selected
ij> select * from (values false) v(b) where nullif(b, true) = false;
B
-----
false
1 row selected
{noformat}
It is the second one that's correct.
> NOT elimination for CASE expressions is broken
> ----------------------------------------------
>
> Key: DERBY-6563
> URL: https://issues.apache.org/jira/browse/DERBY-6563
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.10.2.0
> Reporter: Knut Anders Hatlen
> Assignee: Knut Anders Hatlen
>
> NOT elimination for CASE expressions seems to be broken. Take this example:
> {noformat}
> ij> select * from sysibm.sysdummy1 where not ( case when ibmreqd = 'Y' then
> true else true end );
> IBM&
> ----
> Y
> 1 row selected
> {noformat}
> Both branches of the CASE expression evaluate to TRUE, so one would expect
> the predicate "not ( case ... )" to evaluate to FALSE, and the query should
> return an empty result.
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