Question

The thing is, both tables do have primary keys, and I haven’t had any problems so far with any other standard SELECTS/INSERTS at all. I’m new to JOINS, but I can’t see why this isn’t working.

I’m get this error message:

org.postgresql.util.PSQLException: No primary key found for table devicetable.

However, the primary keys for both tables are the columns I’m selecting for: deviceid / username. Perhaps this has something to do with it?

I’m accessing it via JDBC

PreparedStatement query = curSQL.getConn().prepareStatement("SELECT devicetable.pushid FROM devicetable, usertable WHERE usertable.username=? AND usertable.deviceid = devicetable.deviceid", ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
query.setString(1, username);
ResultSet rs = query.executeQuery();

if (rs.next()){
    rs.updateString("pushid", pushID);
    rs.updateRow();
}

rs.close();
query.close();

With the SQL:

SELECT devicetable.pushid FROM devicetable, usertable
WHERE  usertable.username=?
AND    usertable.deviceID = devicetable.deviceID

Answer 1

Try an explicit join:

SELECT devicetable.pushid
FROM devicetable
JOIN usertable ON usertable.deviceID = devicetable.deviceID
WHERE usertable.username = ?