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From Shyam Sarkar <shyam_sar...@yahoo.com>
Subject Need LOCALTIMESTAMP ?
Date Wed, 11 Feb 2009 22:37:12 GMT
Hello,

Please help me to understand what I am going to implement for Timestamp. Do we need LOCALTIMESTAMP
implementation? See the comparisons below::

=================================================================


LOCALTIMESTAMP
It's often important to get the value of current date and time. Below are the functions used
to do that in the different implementations.

Standard The current timestamp (without time zone) is retrieved with the LOCALTIMESTAMP function
which may be used as: 
SELECT LOCALTIMESTAMP ...
or
SELECT LOCALTIMESTAMP(precision) ...

Note that "SELECT LOCALTIMESTAMP() ..." is illegal: If you don't care about the precision,
then you must not use any parenthesis.

If the DBMS supports the non-core time zone features (feature ID F411), then it must also
provide the functions CURRENT_TIMESTAMP and CURRENT_TIMESTAMP(precision) which return a value
of type TIMESTAMP WITH TIME ZONE. If it doesn't support time zones, then the DBMS must not
provide a CURRENT_TIMESTAMP function.
 
PostgreSQL Follows the standard. 
Documentation
 
DB2 Doesn't have the LOCALTIMESTAMP function. 
Instead, it provides a special, magic value ('special register' in IBM language), CURRENT_TIMESTAMP
(alias to 'CURRENT TIMESTAMP') which may be used as though it were a function without arguments.
However, since DB2 doesn't provide TIMESTAMP WITH TIME ZONE support, the availability of CURRENT_TIMESTAMP
could be said to be against the standard—at least confusing.

Documentation
 
MSSQL Doesn't have the LOCALTIMESTAMP function. 
Instead, it has CURRENT_TIMESTAMP which—however—doesn't return a value of TIMESTAMP WITH
TIME ZONE, but rather a value of MSSQL's DATETIME type (which doesn't contain time zone information).

Documentation
 
MySQL Follows the standard. 
Documentation
 
Oracle Follows the standard. 
Informix On my TODO. 

====================================================================

Thanks,
shyam_sarkar@yahoo.com




      

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