Hi Bala,
I am not sure that this is what you want. However, Derby already has
builtin functions for pi and e. They are called pi() and exp(). So, for
instance, the following statement returns pi and e:
values (pi(), exp(1));
See the Derby reference manual's sections on these builtin functions:
http://db.apache.org/derby/docs/10.11/ref/rrefsqlj29026.html
If you want to use other constants in queries, then I don't know of any
better solution than implementing your own functions to return those
constants. You may want to declare those functions as DETERMINISTIC so
that Derby will know that they can be used in situations which require
constant inputs.
Hope this helps,
-Rick
On 4/24/15 4:15 AM, BalNagendra wrote:
Hi Rick,
Thanks for your advice. I have been able to add some Java libraries
into Derby. It is working fine. Now the question is how to read Java
variables like PI, E into Derby.
thanks and regards
Bala Nagendra
On Wed, Mar 4, 2015 at 2:54 AM, Rick Hillegas-3 [via Apache Database]
<[hidden email] </user/SendEmail.jtp?type=node&node=143967&i=0>> wrote:
On 3/2/15 10:45 PM, BalNagendra wrote:
> Dear All,
>
> I am having the following problem:
>
> Derby is good but functions which are available for database are
not many.
>
> I wanted to dump a character of its Hex value, there was no
function. I had
> to write a Java Program to do the same. It is a tedious process
of loading
> the function JAR to database and they create a database mapping
to it.
>
> Java has rich set of functions under Math, IO and UTIL
libraries. Is there
> any way to use them as Derby Library. I was trying to avoid
mapping each of
> these functions to Derby functions.
>
> Thanks and regards
>
>
>
> --
> View this message in context:
http://apache-database.10148.n7.nabble.com/Derby-How-to-enrich-database-functions-with-Java-Library-tp143832.html
> Sent from the Apache Derby Developers mailing list archive at
Nabble.com.
>
This is an interesting problem. Take a look at the code which
implements
the databaseMetaData optional tool:
http://db.apache.org/derby/docs/10.11/tools/rtoolsoptdbmetadata.html
That code introspects a Java interface and declares functions and
table
functions for all of the methods in the interface.
You may hit some speed bumps with methods which take Object
parameters.
But, provided that those Objects implement Serializable, you
should be
able to declare user-defined types for them.
Hope this helps,
-Rick
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