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Re: [JDBC] Serial data type

From: Kris Jurka <books(at)ejurka.com>
Date: Fri Nov 30 2007 - 06:01:30 EST

On Fri, 30 Nov 2007, Christian Rengstl wrote:

> in my Java app at certain points INSERT queries are built dynamically,
> but now i am facing a problem when the target table contains a SERIAL
> field where NULL values are not allowed. Therefore I have two questions:
>
> 1) How can I find out if there is a serial field in a table, as
> getColumnType() in ResultSetMetaData does not return a field indicating
> SERIAL as far as I could see?

getColumnType returns a value from java.sql.Types, which doesn't have SERIAL so there is no way to return it. ResultSetMetaData.getColumnTypeName() should probably return serial, but it doesn't at the moment. ResultSetMetaData.isAutoIncrement() will work as will DatabaseMetaData.getColumns().

> 2) Why does it not work to issue a query like INSERT INTO
> x(serial_field) VALUES(NULL) as the default of the "serial_field" is
> nextval() anyway?
>

When you've explicitly supplied a value (NULL in this case) the default is not used. Otherwise there would be no way to set a column to NULL that had a default value.

Kris Jurka

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