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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 02:05:12 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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  3)Store column level metadata for collate in Language Layer as well. This will happen in
DataTypeDescriptor(DTD) with the addition of int collateType field. It will be set to 0(UCS_BASIC)/1(TERRITORY_BASED)/-1(UNKNOWN).
There will be get and set methods on DTD for this new field.
  
- 4)The TypeDescriptor for character columns always has 0 for scale because scale does not
apply to character datatypes. Starting Derby 10.3, this scale field in TypeDescriptor will
be overloaded to indicate the collate type of the character. So, if user has requested for
TERRITORY_BASED collation, then the scale in TypeDescriptor for user columns(character) will
be 1(TERRITORY_BASED). The scale will be always 0(UCS_BASIC) for SYS schema character columns
and for databases with collation set to UCS_BASIC.
+ 4)The TypeDescriptor for character columns always has 0 for scale because scale does not
apply to character datatypes. Starting Derby 10.3, this scale field in TypeDescriptor will
be overloaded to indicate the collate type of the character. So, if user has requested for
TERRITORY_BASED collation, then the scale in TypeDescriptor for user columns(character) will
be 1(TERRITORY_BASED). The scale will be always 0(UCS_BASIC) for SYS schema character columns
and for databases with collation set to UCS_BASIC. 
+ 
+ 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.
  
  5)When a character column is added using CREATE TABLE/ALTER TABLE, make sure that the correct
collate type is populated in the TypeDescriptor's scale field in the SYS.SYSCOLUMNS table.
  

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