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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5875) Derby returns wrong results when you set the ESCAPE character to NULL in a LIKE clause.
Date Mon, 23 Jul 2012 13:18:35 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13420636#comment-13420636
] 

Knut Anders Hatlen commented on DERBY-5875:
-------------------------------------------

If the LIKE pattern is parameterized, we raise an error if the ESCAPE character is NULL:

ij> prepare ps as 'select tablename from sys.systables where tablename like ? escape ?';
ij> execute ps using 'values (''SYSD%'', cast(null as char(1)))';
IJ WARNING: Autocommit may close using result set
TABLENAME
--------------------------------------------------------------------------------------------------------------------------------
ERROR 22501: An ESCAPE clause of NULL returns undefined results and is not allowed. (errorCode
= 30000)

I suppose the two cases should behave the same way.
                
> Derby returns wrong results when you set the ESCAPE character to NULL in a LIKE clause.
> ---------------------------------------------------------------------------------------
>
>                 Key: DERBY-5875
>                 URL: https://issues.apache.org/jira/browse/DERBY-5875
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.10.0.0
>            Reporter: Rick Hillegas
>
> The LIKE clause is supposed to evaluate to NULL if the optional ESCAPE character is set
to NULL. Instead, Derby treats this condition as equivalent to omitting the ESCAPE clause.
This violates part 2 of the SQL Standard, section 8.5 <like predicate>, general rule
3.a.ii.
> Thanks to Knut for disclosing this problem via the following script:
> connect 'jdbc:derby:memory:db;create=true';
> prepare ps as 'select tablename from sys.systables where tablename like ''SYSD%'' escape
?';
> -- should return no rows, but actually returns 2
> execute ps using 'values cast( null as char(1) )'; 

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