File APIs for Java Developers
Manipulate DOC, XLS, PPT, PDF and many others from your application.
The moose likes JDBC and Relational Databases and the fly likes Determining null resultset Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login

Win a copy of Java Interview Guide this week in the Jobs Discussion forum!
JavaRanch » Java Forums » Databases » JDBC and Relational Databases
Bookmark "Determining null resultset" Watch "Determining null resultset" New topic

Determining null resultset

Steve Gebert

Joined: May 07, 2004
Posts: 17
Hi - I have my application working and I am now validating user input etc. This application takes the text output of a genetics test and inserts the rows into a Oracle DB. Part of this process requires that I check that a locus name is currently in the database and then look up some genetic information. I am trying to determine if the resultset is null because there was no record. Ie if the text value is "One_CytB26" and the value in the database is "One_CytB_26" then I would expect a null resultset. But how do I check it? Thanks for any help you can give.

private void LookupLocus(String strLocusName)
// this method does a db lookup for each locus to determine the appropriate allele values
DriverManager.registerDriver(new oracle.jdbc.OracleDriver());
String url = "jdbc racle:thin:@db-dbname";
Connection conn = DriverManager.getConnection(url,"usr","pwrd");
Statement stmt = conn.createStatement();
ResultSet rset = stmt.executeQuery("SELECT * FROM AKFINADM.LOCUS_LOOKUP WHERE LOCUS_NAME = '" + strLocusName + "'" );
if(rset == null)
JOptionPane.showMessageDialog(null,"There is a locus error.","SQL Error",JOptionPane.ERROR_MESSAGE);
strPloidy = rset.getString("PLOIDY");
strGenome1 = rset.getString("BOTH_GENOTYPE_1");
strGenome2 = rset.getString("BOTH_GENOTYPE_2");
catch(SQLException e)
JOptionPane.showMessageDialog(null,"There is a database error.","SQL Error",JOptionPane.ERROR_MESSAGE);
catch (Exception e)
[ May 21, 2004: Message edited by: Steve Gebert ]
Jeffrey Hunter
Ranch Hand

Joined: Apr 16, 2004
Posts: 305
The ResultSet will never be null, regardless of whether or not any records were found. A simple implementation of checking the number of records returned is to use an int counter. So, for instance:
Wayne L Johnson
Ranch Hand

Joined: Sep 03, 2003
Posts: 399
If you only expect a single result back, you can use this syntax as well.

[ May 21, 2004: Message edited by: Wayne L Johnson ]
Steve Gebert

Joined: May 07, 2004
Posts: 17
That worked great! I guess I'm still a little used to VB. I appreciate your response, thank you.
Dirk Schreckmann

Joined: Dec 10, 2001
Posts: 7023
Moving this to the JDBC forum...

[How To Ask Good Questions] [JavaRanch FAQ Wiki] [JavaRanch Radio]
Srinivas Gogineni

Joined: May 06, 2004
Posts: 6
You can try using the wasNull method of the resultset

Thx and regards
Consider Paul's rocket mass heater.
subject: Determining null resultset
It's not a secret anymore!