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Re: Getting the size of a result set

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El jueves, 8 de marzo de 2001, 18:02:04 (UTC+1), Valentin Todorov  escribió:
> Try this:
> 
>     long getCount(Connection con, String table){
>         Statement stmt = null;
>         ResultSet rs = null;
>         int count = 0;
>         try{
>             stmt = con.createStatement();
>             rs = stmt.executeQuery("SELECT COUNT(*) FROM "+table);
>             if(rs.next())
>                 count = rs.getInt(1);
>         }catch(SQLException e) {
>             // error handling
>         }finally{
>             // close rs &stmt
>         }
>     }
> 
> HTH
> Valentin
> 
> 
> Jon Skeet schrieb:
> 
> > Hi everyone,
> >
> > I'm not new to Java, but I'm extremely new to JDBC, SQL, and the whole
> > database "thang". I've been tasked with writing a class to implement our
> > own data interface, but accessing a JDBC database. One of the methods I
> > have to implement is (on a ResultSet-type object) getCount() which
> > should return the number of rows in the results.
> >
> > I've been trying to figure out a way of doing this using JDBC, and I
> > haven't got very far yet. As this is only a prototype at the moment, I'm
> > probably okay to use any standard JDBC extensions etc if necessary,
> > although obviously I'd like to keep it as simple as possible. I'd hoped
> > that ResultSetMetaData would have something in it, or that I could
> > specify an OUT parameter in a PreparedStatement which could contain the
> > count. (I realise I can use OUT parameters with a CallableStatement, but
> > I can't force our users to add appropriate CallableStatements,
> > unfortunately.) I can get the count if I don't specify anything else,
> > but I really need the rest of the data as well...
> >
> > I realise this may be an impossible mission, but I thought it would be
> > worth asking.
> >
> > --
> > Jon Skeet - skeet@pobox.com
> > http://www.pobox.com/~skeet

Hi, if you want to make a count of rows is better always use COUNT(1) than
COUNT(*). Because the * implies project all the atributes and the 1 avoid project the attributes.

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Re: Getting the size of a result set jagilberte@gmail.com - 2016-02-15 09:15 -0800
  Re: Getting the size of a result set Arne Vajhøj <arne@vajhoej.dk> - 2016-02-15 12:53 -0500
  Re: Getting the size of a result set Rhino <no_offline_contact@example.com> - 2016-10-16 21:49 -0400
    Re: Getting the size of a result set Arne Vajhøj <arne@vajhoej.dk> - 2016-10-19 23:50 -0400

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