Row Fixture also supports functions, so you can check on the objects that you query. For example, lets say that we have a database of employee objects. We want to test that the employees were paid correctly.

fitnesse.fixtures.EmployeePayRecordsRowFixture
id pay()
1 1000
2 2000

As you can see, we query the employees by id, and then check to see that their pay was correct. Here's what it would look like if their pay was not correct.

fitnesse.fixtures.EmployeePayRecordsRowFixture
id pay()
1 1000
2 3000

And here is what it would look like if there were missing or extra employees

fitnesse.fixtures.EmployeePayRecordsRowFixture
id pay()
1 1000
5 5000

Here is the code for the fixtures:
package fitnesse.fixtures;

import fit.RowFixture;

public class EmployeePayRecordsRowFixture extends RowFixture  {
  public Object[] query() throws Exception {
    EmployeePayRecord[] records = new EmployeePayRecord[2];
    records[0] = new EmployeePayRecord(1, 1000);
    records[1] = new EmployeePayRecord(2,2000);
    return records;
  }
  public Class getTargetClass() {
    return EmployeePayRecord.class;
  }
} 
package fitnesse.fixtures;

public class EmployeePayRecord {
  public int id;
  private double salary;
  public EmployeePayRecord(int id, double salary) {
    this.id = id;
    this.salary = salary;
  }
  public double pay() {
    return salary;
  }
}


For more about Row Fixture see Row Fixture Multiple Keys