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https://issues.apache.org/jira/browse/DERBY-2335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12495206
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Mamta A. Satoor commented on DERBY-2335:
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I missed that CharConstantNode (and every QueryTreeNode) has a
getLanguageConnection() method. I will go ahead and fix that in next patch.
> Compare character datatypes with different collation ordering.
> --------------------------------------------------------------
>
> Key: DERBY-2335
> URL: https://issues.apache.org/jira/browse/DERBY-2335
> Project: Derby
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 10.3.0.0
> Reporter: Mamta A. Satoor
> Assigned To: Mamta A. Satoor
> Attachments:
> DERBY2335_correct_collation_for_constants_persistent_column_v1_diff.txt,
> DERBY2335_correct_collation_for_constants_persistent_column_v1_stat.txt,
> DERBY2335_fix_stringCompare_Method_CollatorSQLxxx_classes_v1_diff.txt,
> DERBY2335_fix_stringCompare_Method_CollatorSQLxxx_classes_v1_stat.txt,
> DERBY2335_More_tests_And_Fix_getNull_v1_diff.txt,
> DERBY2335_More_tests_And_Fix_getNull_v1_stat.txt
>
>
> The parent task DERBY-1478 will enable users to have a different collation
> order for user-defined character datatypes compared to UNICODE based
> collation, UCS_BASIC, used by system tables. This sub-task is added to handle
> the case where a comparison is made between character datatypes with
> different collation order.
> For instance
> Let's say, a database is created to use a territory based collation for
> character types. And say there is a userSchema schema in that database which
> has a table tableInfo with column tablename defined as VARCHAR. This
> tableInfo.tablename will have territory based collation assoicated with it.
> And say this column is then compared with a VARCHAR column in SYS schema,
> then how will the comparison happen, since the 2 columns being compared have
> different collation associated with them?
> select * from sys.systables and userSchema.tableInfo where
> systables.tablename = tableInfo,tablename
> Thanks to Rick for taking the time out on this issue. He had following
> suggestion
> </Rick comment start>
> "As I read part 2 of the SQL Standard, it looks like you need a CAST in order
> to compare 2 strings which have different collations bound to them. Both
> string operands must have the same collation--that is my reading of Syntax
> rule 3b in section 9.13. Sections 6.12 and 6.1 explain how to cast the
> operands so that you can compare them. I think you need to write an
> expression like this:
> WHERE userStringCol = CAST ( systemStringCol AS VARCHAR COLLATE
> userStringColumnsCollation )
> Here's an example I googled up:
> http://docs.openlinksw.com/virtuoso/sqlrefDATATYPES.html. Hope this helps.
> </Rick comment end>
> When this task is taken up, it would be good to explore Rick's suggestion.
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