write below code in constructor
DefaultTableModel model;
model = new DefaultTableModel(null,col);
jTable1.setModel(model);
int l2 = jTable1.getRowCount();
while(l2>=1)
{
model.removeRow(0);
l2 = l2-1;
}
and after retrieving values from database
String data[]={value1,value2};
model.addRow(data);