问题:

I have to perform a bulk update on a table. Making a fast example :

 UPDATE Book b SET b.amount = b.amount + 1 WHERE b IN ( :books )

The problem is that b.amount can be or a NULL value or an int, and if there is a NULL value it should behave as b.amount would be equal to 1.

Is there any "cast" in JPA/JPQL or any other way to work-around this problem,

Thank you in advance,

Regards, P

回答1:

You should be able to use COALESCE:

UPDATE Book b SET b.amount = COALESCE(b.amount, 1) + 1 WHERE b IN ( :books )

回答2:

I would go and fix the nulls first with a separate query:

UPDATE Book set b.amount = 0 WHERE b.amount IS NULL

And also make it impossible to insert null, if it is not a legal value for your logic. For example have it @Column(nullable=false)

回答3:

I used the following way to get the JDBC connection from the current JPA provider.

SessionImplementor si = (SessionImplementor) em.unwrap(Session.class);
Connection connection = si.getJdbcConnectionAccess().obtainConnection();
PreparedStatement pstmt = connection.prepareStatement("...");
// Do something
pstmt.addBatch();
pstmt.executeBatch();
si.getJdbcConnectionAccess().releaseConnection(connection);