Quering the ResultSet

[kunal Jaggi]

I am using Tomcat 4.1.12 on Windows 2000 professional. I am using the JDBC-ODBC Bridge driver to access the MS Access Database. I am having a problem while quering the ResultSet. Following is the code snippet that gives the problem :-
try{
rs=st.executeQuery("SELECT * FROM Users WHERE cID='"+f.getUserName()+"'");
if(rs==null)
userExists=false;
else
userExists=true;
}catch(SQLException e){
System.err.println(e);
}
I have checked the database, I know that there is no user id foe example “kunal”- even then the boolean variables evaluates to true. Can we query the ResultSet like that?
Regards,
Kunal Jaggi
Sun Certified Java 2 Programmer

[Dirk Schreckmann]

Java Facier,
Welcome to JavaRanch! We ain't got many rules 'round these parts, but we do got one. Please change your display name to comply with The JavaRanch Naming Policy.
Thanks pardner. Hope to see you 'round the Ranch!

[Lasse Koskela]

The ResultSet object returned by executeQuery() is never null. If there are no matching records, an empty ResultSet is returned.
Thus, you need to do something like this instead:

try {
  rs = st.executeQuery("SELECT * FROM Users WHERE cID='"+f.getUserName()+"'");
  // rs.next() moves the "cursor" to the first returned record
  if (rs.next()) {
    userExists = true;
  } else {
    userExists = false;
  }
}catch(SQLException e) {
  System.err.println(e);
}

[Dirk Schreckmann]

kunal_jaggi,
Thanks for changing your display name. Now, if you could just replace the underscore with a space, our naming policy would be satisfied.
Thanks.

[Jeanne Boyarsky]

The above example, could even be shorter. Checking for an empty result set is fast and easy.

try {
  rs = st.executeQuery("SELECT * FROM Users WHERE cID='"+f.getUserName()+"'");
  userExists = rs.next();
}catch(SQLException e) {
  System.err.println(e);
}

[Kunal Goel]

Thanks Lasse and Jeanne, it was something very obvious that I missed.