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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Closed: (DERBY-2524) 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.
Date Mon, 14 May 2007 17:19:17 GMT

     [ https://issues.apache.org/jira/browse/DERBY-2524?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Mamta A. Satoor closed DERBY-2524.
----------------------------------


> 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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