Hi again Boerries,
Ludwig, Boerries wrote:
> Hi,
>
> I have a similar problem. My application allows the administrator to query
> the database with SQL-statements. I had my own connections to HSQL, but now
> I get "java.sql.SQLException: The database is already in use by another
> process". The other process ist OJB.
AFAIK HSQLDB does only allow single user access. You must run it in
server mode to allow multiple clients.
>
> My questions are:
>
> 1. can I pass SQL-statements to OJB (the solution from Jakob does not help)
Yes. There is a QueryBySQL class that allows freeform SQL.
1. If you use such a QueryBySQL q with a PB.getCollectionByQuery(q) the
class specified is used to materialize concrete instances filled from
the resultset of the query. Thus the columns of the sql statement must
match the class-descriptor layout for that class.
2. If you use it within a PB.getReportQueryIteratorByQuery(q) the class
is ignored. Thus the SQL does *not* need to match the class layout!
> 2. can I reuse a connection from OJBs connetion-pool to pass my query to
>
Yes. Have a look at the org.apacha.ojb.PerformanceJdbcReferenceTest to
see how this is done.
cheers,
Thomas
> Thanks in advance
>
> Boerries
>
> .............................
>
> hi ronen,
>
> you could also use a report query to retrieve simple column data:
>
> crit = new Criteria();
> crit.addEqualTo("name", "%er");
> query = new ReportQueryByCriteria(Person.class, crit);
> query.setColumns(new String[] { "sum(test)" });
> broker.getReportQueryIteratorByQuery(query);
>
> hth
> jakob
>
> ----- Original Message -----
> From: <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Wednesday, August 07, 2002 2:32 PM
> Subject: Simple SQL Query
>
>
>
>>Hello everyone.
>>
>>i have a quick question which i'm sure you guys would know.
>>In my database, I have a table called "PRODUCTS" which has a column called
>>"ID". (this table maps to the persistent class Product.java). What i'm
>>simply trying to do is to use an sql statement to find out how many
>>products there are in the "PRODUCTS" table.
>>
>>The code I am using is:
>>
>>Criteria criteria = new Criteria();
>>criteria.addSql( "SELECT COUNT(ID) FROM PRODUCTS;" );
>>
>>The problem is that this sql statement should simply return a number, and
>>not an instance of the persistent class Product.java. However, it seems
>
> to
>
>>me like every Query object must be passed a persistent class which is to
>
> be
>
>>populated. In other words, the first parameter of every Query object
>
> (e.g.
>
>>QueryByCriteria, QueryBySQL, etc) has to be a persistent class.
>>
>>I have tried using Integer.class as the first parameter, but i receive a
>>ClassNotPersistenceCapableException.
>>
>>
>>Does anyone know how to handle such a simple request?
>>
>>Thanks for your help and time.
>>Ronen.
>>
>>
>
>
> --
> To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]>
> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
>
>
>
>
--
To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]>
For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
