Rick Hillegas wrote:
Hi Mamta,
Thanks for this extensive write-up. This helps me puzzle through the
issues although I'm afraid I'm still muddled. Some comments follow inline.
Same here.
Mamta Satoor wrote:
lots of good stuff ...
+1
I think we should avoid violating
the SQL standard if we can.
+1
In looking at this I was wondering if it would be useful if it could be
described in terms of SQL Standard constructs how the system columns
come to have a different collation. E.g. is it as though they are
declared at the column level with a <collate clause>, or is it as though
the system schemas are declared with a different character set to the
user schemas?
Would this make a difference in how a string literal or other character
expressions are collated?
For string literals
5.3 SR15) says the collation is the character set collation, and then
5.3 SR14b) says the character set is the the character set of the
SQL-client module that contains the <character string literal>.
So here's it's unclear to me what 'SQL-client module' means in a derby
context.
For a function (or any other declared character type except column
definitions) the collation will come from its data type, which goes to
6.1 SR3b) and 6.1 SR16), which says implementation defined character set.
For a column definition then 11.4 SR10b) specifies the character set as
being the schema's character set.
Thus Derby could have two character sets:
- USER - UCS repertoire with default collation of UCS_BASIC or
UNICODE depending on value of collation JDBC attribute at create
database time
- SYSTEM - UCS repertoire with default collation of UCS_BASIC
When a schema is created it is implementation defined as to its
character set (if one is not defined) 11.1 SR5)
So Derby's implementation could be:
user schemas have a character set of USER
system schemas have a character set of SYSTEM
Then ...
- columns would have the required collation (11.4 SR10b))
- functions (& others) would have the required collation (Derby's
implementation could be to pick the schema character set)
which leaves string literals as the issue, what is a 'SQL-client module'?
Dan.
