Hello,
If you want to do this with a user-defined function, then you will need
to declare a separate function for each datatype you need to handle.
You might be able to use a CASE expression for this problem. It's a
little more verbose than using a function. Here is an example:
connect 'jdbc:derby:memory:derby;create=true';
create table t( a int, b int, c date, d date );
insert into t( b, d ) values ( 1, date('1994-02-23') );
select
case when a is null then b else a end,
case when c is null then d else c end
from t;
Hope this helps,
-Rick
Hardie82 wrote:
Hi,
I want to implement the NVL-function for my derby-db to use sql-statement
once written for an informix-db. Therefor I began to write a function class
with methods like the following code:
public static String nvl(String arg1, String arg2)
{
if(arg1 == null)
return arg2;
return arg1;
}
I also create a function in sql:
CREATE FUNCTION NVL(arg1 VARCHAR(100), arg2 VARCCHAR(100)) returns
VARCHAR(100) language java
external name 'mypackage.testdb.DerbyCustomFunctions.nvl' parameter style
java no sql;
That works fine for statements with varchar-argument and length 100. But
what about other data-types like INTEGER or DATE? Have I to implement
methods for all data-type combination or is there a better way? Something
like a data-type converter for derby? I thought to get informations for
implementation from the nullif-function but can't find it in the derby-code.
