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From "Amit Handa (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-113) Comparison does not perform implicit type conversion
Date Tue, 11 Jan 2005 05:00:17 GMT
     [ http://issues.apache.org/jira/browse/DERBY-113?page=comments#action_57490 ]
     
Amit Handa commented on DERBY-113:
----------------------------------

First, this was filed by Jeremy as a separate bug coming out from Derby-7 bug.
So we need to understand how promotion happens(read built in broadening) when two differrent
datatypes are compared as part of a function say NULLIF(A,B). A, B are two differrent types.

Otherwise also as Jeremy points out select * from dual where '1' = 1; 
if we compare where a defined function is not involved, how the datatypes should behave.

[1] can give help about datatypes and promotions but is not very explicit or in detail.
Also see [2] where I have commenetd on built in broadening according to types compared.

[1] http://incubator.apache.org/derby/manuals/reference/sqlj122.html#HDRSII-SQLJ-31068
[2] http://issues.apache.org/jira/browse/DERBY-7

Further the derby documentation uses terms like built in broadening at places but is not very
explicit. If we are clear on that, I guess it can lead to a solution for this.
Just some pointers which can help lead to a solution.

> Comparison does not perform implicit type conversion
> ----------------------------------------------------
>
>          Key: DERBY-113
>          URL: http://issues.apache.org/jira/browse/DERBY-113
>      Project: Derby
>         Type: Bug
>   Components: SQL
>     Reporter: Jeremy Boynes

>
> The operands to a comparision operator are not implictly converted to the dominant type
resulting in an unexpected exception:
> For example:
> ij> select * from dual where '1' = 1;
> ERROR 42818: Comparisons between 'CHAR' and 'INTEGER' are not supported.
> fails whereas
> ij> select * from dual where cast('1' as int) = 1;
> DUM&
> ----
> X
> works. The type escalation should be implicit.

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