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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4658) Allow explicit casts of string values to BOOLEAN
Date Thu, 17 Jun 2010 15:36:23 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4658?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12879809#action_12879809

Rick Hillegas commented on DERBY-4658:

Hi Knut. Thanks for taking a look at the new patch. I don't think that the changes in BooleanConstantNode
affect the line in CastNode which you're referring to. The problem there is that the nullability
of the CastNode is copied from the nullability of the source cast operand. In the following

  cast ( 'unknown' as boolean )

the source operand is a string constant which is not nullable, but the result of the cast
is nullable--in fact, it is NULL.

> Allow explicit casts of string values to BOOLEAN
> ------------------------------------------------
>                 Key: DERBY-4658
>                 URL: https://issues.apache.org/jira/browse/DERBY-4658
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Rick Hillegas
>            Assignee: Rick Hillegas
>         Attachments: derby-4658-01-aa-booleanCasts.diff, derby-4658-01-ab-booleanCasts.diff
> The SQL Standard allows strings to be explicitly cast to BOOLEAN values. Strings are
the only type (other than BOOLEAN itself) which can be cast to BOOLEAN. As part of our expanding
support for the BOOLEAN datatype, we should allow these casts.
> Casting string types to boolean is defined by part 2, section 6.12 (<cast specification>),
general rule 20:
> a) Trim whitespace off the string
> b) Then apply the rules in section 5.3 (<literal>). This means that the trimmed
string must be 'TRUE', 'FALSE', or 'UNKNOWN', regardless of case.
> c) Otherwise, raise an exception.

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