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From "Bernt M. Johnsen (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-1231) LIKE does not match empty strings when used with a prepared statement
Date Tue, 05 Dec 2006 07:51:22 GMT
     [ http://issues.apache.org/jira/browse/DERBY-1231?page=all ]

Bernt M. Johnsen updated DERBY-1231:
------------------------------------

    Attachment: DERBY-1231.diff

Simple fix to Like.lessThanString. It should not return null when the pattern has zero length,
but proceed to the comparision logic.

Another small issue caught while studying the logic of this. Like.isOptimizable should return
true if the pattern has zero length. Slight optimization if the user does a lot of blabla
LIKE ''

QUESTION: Is the tweak in the second last line in metadata.properties:
      AND (V."COLUMN_NAME" LIKE ? OR V."COLUMN_NAME" = ?) \
a consequence of this bug and could now be changed to
      AND V."COLUMN_NAME" LIKE ? \
is part of this fix?



> LIKE does not match empty strings when used with a prepared statement
> ---------------------------------------------------------------------
>
>                 Key: DERBY-1231
>                 URL: http://issues.apache.org/jira/browse/DERBY-1231
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC, SQL
>    Affects Versions: 10.2.1.6, 10.1.2.1, 10.3.0.0, 10.1.3.1
>            Reporter: Dyre Tjeldvoll
>         Assigned To: Bernt M. Johnsen
>             Fix For: 10.2.2.0
>
>         Attachments: DERBY-1231.diff, vti.java
>
>
> LIKE should give true for two 0-length strings. See SQL 2003 Ch. 8.5
> General Rules 3)c)i)
> The query SELECT * FROM t WHERE v like ''
> appears to give me all rows where v is an empty
> string, as expected.
> But a prepared statement
> SELECT * FROM t WHERE v like ?, with setString(1, "")
> always returns an empty result set. See attached repro for the full example.

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