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https://issues.apache.org/jira/browse/DERBY-2524?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mamta A. Satoor resolved DERBY-2524.
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Resolution: Fixed
> DataTypeDescriptor(DTD) needs to have collation type and collation
> derivation. These new fields will apply only for character string types.
> Other types should ignore them.
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-2524
> URL: https://issues.apache.org/jira/browse/DERBY-2524
> Project: Derby
> Issue Type: New Feature
> Components: SQL
> Affects Versions: 10.3.0.0
> Reporter: Mamta A. Satoor
> Assigned To: Mamta A. Satoor
> Attachments: DERBY2524_Collation_Info_In_DTD_v1_diff.txt,
> DERBY2524_Collation_Info_In_DTD_v1_stat.txt,
> DERBY2524_Collation_Info_In_DTD_v2_diff.txt,
> DERBY2524_Collation_Info_In_DTD_v2_stat.txt,
> DERBY2524_ignore_collation_for_nonchar_v1_diff.txt,
> DERBY2524_ignore_collation_for_nonchar_v1_stat.txt
>
>
> This the one of the ground works for getting different kinds of collations
> working for character string types. More information on this project can be
> found at
> http://wiki.apache.org/db-derby/BuiltInLanguageBasedOrderingDERBY-1478.
> Basically, all the types in Derby have a DTD associated with them. For
> character string types, these DTDs should have valid values for collation
> derivation and collation type. For other data types, these 2 fields do not
> apply and should be ignored.
> SQL spec talks about character string types having collation type and
> collation derivation associated with them (SQL spec Section 4.2.2 Comparison
> of character strings). If collation derivation says explicit or implicit,
> then it means that there is a valid collation type associated with the
> charcter string type. If the collation derivation is none, then it means that
> collation type can't be established for the character string type.
> 1)Collation derivation will be explicit if COLLATE clause has been used for
> character string type (this is not a possibility for Derby 10.3, because we
> are not planning to support SQL COLLATE clause in this release).
> 2)Collation derivation will be implicit if the collation can be determined
> w/o the COLLATE clause eg CREATE TABLE t1(c11 char(4)) then c11 will have
> collation of USER character set. Another eg, TRIM(c11) then the result
> character string of TRIM operation will have collation of the operand, c11.
> 3)Collation derivation will be none if the aggregate methods are dealing with
> character strings with different collations (Section 9.3 Data types of
> results of aggregations Syntax Rule 3aii).
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