Oracle vs. Hypersonic SQL

Question

I need to select by date in a SQL query, for example

SELECT * FROM foo WHERE date = '2009-09-09'

That query works in my Hypersonic test database, but not Oracle, which seems to requires:

SELECT * FROM foo WHERE date = TO_DATE('2009-09-09', 'yyyy-mm-dd')

Is there a way to select by date uniformly across these two databases?

Answer 1

You could try H2 database as your in memory database (http://www.h2database.com). It should have decent Oracle compablity mode.

Answer 2

A "date = 'literal string'" predicate in Oracle is usually not recommended - it is sensitive to NLS_DATE_FORMAT settings and often leads to misunderstanding on what you're looking for in a result set (in your example above do you want all records for the day or just those created exactly at midnight?)

If you need a uniform query string for both databases, you might rename the table in Oracle and create a view with the name foo and cast the date datatype to varchar2 in the view logic. You'll probably need to add a function-based index to the table to allow efficient searching on the recast value.

Answer 3

I found the answer - you can create the TO_DATE function in HyperSonic and then the second query works in both. For example, make the class:

public class Date {
    public static String toDate( String value, String format ) {
        return value;
    }
}

And the query

SELECT * FROM foo WHERE date = TO_DATE('2009-09-09', 'yyyy-mm-dd')

works in both.

Answer 4

If you can, you can set your NLS_DATE_FORMAT in Oracle session, that way you do not need to use the TO_DATE function, oracle will do this for you behind the scenes.

SQL> select value from v$nls_parameters where parameter = 'NLS_DATE_FORMAT';

VALUE
----------------------------------------------------------------
DD/MM/YYYY

SQL> create table nls_date_test ( id number(10) , date_entered date );

Table created.

SQL> insert into nls_date_test values ( 1 , '31/05/2009' );

1 row created.

SQL> insert into nls_date_test values ( 2 , '30/05/2009' );

1 row created.

SQL> select * from nls_date_test where date_entered = '2009-09-09';
select * from nls_date_test where date_entered = '2009-09-09'
                                                  *
ERROR at line 1:
ORA-01861: literal does not match format string


SQL> alter session set nls_date_format = 'YYYY-MM-DD';

Session altered.

SQL> select * from nls_date_test where date_entered = '2009-05-30';

        ID DATE_ENTER
---------- ----------
         2 2009-05-30

SQL> select value from v$nls_parameters where parameter = 'NLS_DATE_FORMAT';

VALUE
----------------------------------------------------------------
YYYY-MM-DD

SQL>