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https://issues.apache.org/jira/browse/DERBY-6584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14008922#comment-14008922
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Bryan Pendleton commented on DERBY-6584:
----------------------------------------
Sometimes, restrictions and behaviors like these were added for DB2
compatibility prior to the open-sourcing of Derby, in which case it seems like
it would be fine to alter the behavior for improved consistency.
> Comparisons between BOOLEAN and other types sometimes succeed
> -------------------------------------------------------------
>
> Key: DERBY-6584
> URL: https://issues.apache.org/jira/browse/DERBY-6584
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.10.2.0
> Reporter: Knut Anders Hatlen
>
> I would have expected the following queries to fail because of type mismatch
> between CHAR and BOOLEAN:
> {noformat}
> ij> values 'abc' = true, true = 'xyz', false = 'yes';
> 1
> -----
> true
> true
> false
> 3 rows selected
> ij> values 'abc' in (true, false), true in ('abc', 'def');
> 1
> -----
> true
> true
> 2 rows selected
> {noformat}
> Similar queries using INTEGER values instead of CHAR values fail as expected:
> {noformat}
> ij> values 1 = true;
> ERROR 42818: Comparisons between 'INTEGER' and 'BOOLEAN' are not supported.
> Types must be comparable. String types must also have matching collation. If
> collation does not match, a possible solution is to cast operands to force
> them to the default collation (e.g. SELECT tablename FROM sys.systables WHERE
> CAST(tablename AS VARCHAR(128)) = 'T1')
> ij> values true = 1;
> ERROR 42818: Comparisons between 'BOOLEAN' and 'INTEGER' are not supported.
> Types must be comparable. String types must also have matching collation. If
> collation does not match, a possible solution is to cast operands to force
> them to the default collation (e.g. SELECT tablename FROM sys.systables WHERE
> CAST(tablename AS VARCHAR(128)) = 'T1')
> ij> values true in (1,2,3);
> ERROR 42818: Comparisons between 'BOOLEAN' and 'INTEGER' are not supported.
> Types must be comparable. String types must also have matching collation. If
> collation does not match, a possible solution is to cast operands to force
> them to the default collation (e.g. SELECT tablename FROM sys.systables WHERE
> CAST(tablename AS VARCHAR(128)) = 'T1')
> ij> values 1 in (true, false);
> ERROR 42818: Comparisons between 'INTEGER' and 'BOOLEAN' are not supported.
> Types must be comparable. String types must also have matching collation. If
> collation does not match, a possible solution is to cast operands to force
> them to the default collation (e.g. SELECT tablename FROM sys.systables WHERE
> CAST(tablename AS VARCHAR(128)) = 'T1')
> {noformat}
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