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https://issues.apache.org/jira/browse/DERBY-6363?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13783872#comment-13783872
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Knut Anders Hatlen commented on DERBY-6363:
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It looks like something goes wrong during conversion of the OR expression to an
IN list in OrNode.preprocess(), and {{( b = 'a' or b = 'b' )}} gets incorrectly
converted to {{( b IN ('a') )}}.
I think the problem may be that OrNode.preprocess() expects the OrNode to be on
conjunctive normal form. Currently, only WHERE, HAVING and ON clauses are
converted to CNF, as far as I can see. (And the expression indeed evaluates to
the correct value if it is moved from the SELECT list to a WHERE clause.)
> Incorrect evaluation of logical expressions in CASE
> ---------------------------------------------------
>
> Key: DERBY-6363
> URL: https://issues.apache.org/jira/browse/DERBY-6363
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.4.1.3, 10.8.3.0, 10.10.1.1
> Reporter: Grzegorz Żur
> Attachments: ac4d3680a5x0141x78ccx0cb1x000006c347101.java
>
>
> Logical expressions with AND and OR operators inside WHEN inside CASE
> expression nested in SELECT part of statement are wrongly evaluated.
> Evaluation results depends on position of OR subexpression. If OR is placed
> on left side of AND it is evaluated incorrectly.
> Following code shows the error.
> create table t ( a int, b char );
> insert into t values (1, 'a');
> insert into t values (2, 'b');
> insert into t values (3, 'a');
> insert into t values (4, 'b');
> insert into t values (5, 'a');
> insert into t values (6, 'b');
> select
> a,
> b,
> case
> when (( b = 'a' or b = 'b' ) and a < 4) then 'x'
> else '-'
> end,
> case
> when (a < 4 and ( b = 'a' or b = 'b' )) then 'y'
> else '-'
> end
> from t;
> Actual result:
> 1 a x y
> 2 b - y
> 3 a x y
> 4 b - -
> 5 a - -
> 6 b - -
> Expected result
> 1 a x y
> 2 b x y
> 3 a x y
> 4 b - -
> 5 a - -
> 6 b - -
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