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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-3975) SELECT DISTINCT may return duplicates with territory-based collation
Date Fri, 05 Dec 2008 16:38:44 GMT
SELECT DISTINCT may return duplicates with territory-based collation
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                 Key: DERBY-3975
                 URL: https://issues.apache.org/jira/browse/DERBY-3975
             Project: Derby
          Issue Type: Bug
          Components: SQL
    Affects Versions: 10.4.2.0
            Reporter: Knut Anders Hatlen


I defined my own locale (en_US_aisb) where the collation rules said that a=b. When I tried
queries with SELECT DISTINCT, they didn't always eliminate all duplicates. Here's an example:

ij> connect 'jdbc:derby:db;create=true;territory=en_US_aisb;collation=TERRITORY_BASED';
ij> create table t (x varchar(10));
0 rows inserted/updated/deleted
ij> insert into t values 'a','b','abba','baab','ABBA';
5 rows inserted/updated/deleted
ij> select distinct * from t;
X         
----------
ABBA      
b         
a         
abba      

4 rows selected
ij> select distinct * from t order by x;
X         
----------
a         
abba      
ABBA      

3 rows selected

The first query did eliminate the duplicate "abba"/"baab", but it did not eliminate the duplicate
"a"/"b". When an ORDER BY clause was added (the second query), all the duplicates were eliminated.

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