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From "Lukas Eder (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-5006) Handle NULL literals like any other database
Date Sun, 06 Feb 2011 09:12:30 GMT
Handle NULL literals like any other database
--------------------------------------------

                 Key: DERBY-5006
                 URL: https://issues.apache.org/jira/browse/DERBY-5006
             Project: Derby
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 10.7.1.1
            Reporter: Lukas Eder
            Priority: Minor


Most RDMBS allow for typeless NULL values / literals just about anywhere in a SQL statement.
I am not aware of SQL standards explicitly encouraging the enforcement of casts on NULL values
and literals. Even DB2, the "mother of strongly typed databases" has finally given up type
enforcement on NULL values / literals in version 9.7:
http://publib.boulder.ibm.com/infocenter/db2luw/v9r7/index.jsp?topic=/com.ibm.db2.luw.wn.doc/doc/i0054263.html

I wonder, whether this would be a nice way to go for Derby as well? I am asking this from
the perspective of a database abstraction library developer (http://jooq.sourceforge.net).
I find it extremely difficult to cast NULL values to the correct type in every occasion, as
in Java, null does not have a type. A good example for this is:

SELECT cast(null as ...) FROM SYSIBM.SYSDUMMY1

>From the Java application's point of view, any type is OK, because it won't matter. But
then, why would it matter to Derby?
Another good example to me is this:

INSERT INTO X (ID, NAME, NUMBER) 
SELECT (10, null, null)
FROM SYSIBM.SYSDUMMY1

This won't work. I'll need to rewrite it to something like this:

INSERT INTO X (ID, NAME, NUMBER) 
SELECT (10, CAST(null AS VARCHAR(100)), CAST(null AS INTEGER))
FROM SYSIBM.SYSDUMMY1

When actually Derby could infer the types of null. Type inference is done sometimes. This
will work:

INSERT INTO X (ID, NAME, NUMBER)
VALUES (10, null, null)

What do you guys think?

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