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From Apache Wiki <wikidi...@apache.org>
Subject [Db-derby Wiki] Update of "BuiltInLanguageBasedOrderingDERBY-1478" by MamtaSatoor
Date Thu, 22 Mar 2007 15:08:06 GMT
Dear Wiki user,

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The following page has been changed by MamtaSatoor:
http://wiki.apache.org/db-derby/BuiltInLanguageBasedOrderingDERBY-1478

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  5)The type definition of a column is described by DTD (DataTypeDescriptor). This DTD will
have an additional attribute called collation type. The correct assoication of collation to
the DTD for system or user columns is easy and it will happen at bind time. But there are
other character expressions who are either string literals, or result of cast, trim, upper,
lower, substring, concatenate etc. Determining their collation type requires special handling.
  
- 6)For a string literal which is not inside an operation like upper/lower/substring etc,
it's collation type in DTD will be marked UNKNOWN. When such a string literal gets used in
a collation method, it's collation type will be same as the other operand involved in the
collation eg sysColumn1 < 'aaa', then the collation type of 'aaa' will change from UNKNOWN
to UCS_LOCALE at the comparison time. But if the comparison was userColumn1 < 'aaa', then
the collation type of 'aaa' will be that of the collaiton type of userColumn1. As a third
case, if the comparison was between 2 string literals, ie 'aaa' < 'bbb', then the collation
type of each of the string literal will be the COLLATION applicable at the user character
level.
+ 6)For a string literal which is not inside an operation like upper/lower/substring etc,
it's collation type in DTD will be marked UNKNOWN. When such a string literal gets used in
a collation method, it's collation type will be same as the other operand involved in the
collation eg sysColumn1 < 'aaa', then the collation type of 'aaa' will change from UNKNOWN
to UCS_BASIC at the comparison time. But if the comparison was userColumn1 < 'aaa', then
the collation type of 'aaa' will be that of the collaiton type of userColumn1. As a third
case, if the comparison was between 2 string literals, ie 'aaa' < 'bbb', then the collation
type of each of the string literal will be the COLLATION applicable at the user character
level.
  
     '''Question''' Does this match the SQL standard?
  

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