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https://issues.apache.org/jira/browse/DERBY-6569?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Knut Anders Hatlen updated DERBY-6569:
--------------------------------------
Labels: derby_backport_reject_10_11 (was: )
Marking as not for backport. Since the fix only affects queries whose behaviour
is undefined by the standard, backporting it doesn't sound worthwhile.
> NULLIF may return incorrect results if first operand calls non-deterministic
> function
> -------------------------------------------------------------------------------------
>
> Key: DERBY-6569
> URL: https://issues.apache.org/jira/browse/DERBY-6569
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.10.2.0
> Reporter: Knut Anders Hatlen
> Assignee: Knut Anders Hatlen
> Labels: derby_backport_reject_10_11
> Fix For: 10.12.0.0
>
> Attachments: d6569-1a.diff, d6569-1b.diff
>
>
> The SQL standard doesn't allow non-deterministic function calls in the
> operands of NULLIF. Derby does however allow such calls, but the results may
> not be as one might expect.
> Take an expression such as NULLIF(expr, 1). It shouldn't ever return 1. If
> expr is 1, it should return NULL, and if expr is not 1, it should return expr.
> If expr contains a call to a non-deterministic function, it may actually end
> up returning 1 sometimes:
> {noformat}
> ij> SELECT NULLIF(INT(RANDOM()*2), 1) FROM SYS.SYSTABLES;
> 1
> -----------
> 1
> 1
> 1
> NULL
> NULL
> NULL
> NULL
> 0
> 1
> NULL
> NULL
> 0
> 0
> NULL
> 0
> 1
> 0
> NULL
> 1
> 0
> NULL
> NULL
> NULL
> 23 rows selected
> {noformat}
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