如何检查列中是否存在特定数据

Question

I am working on java swing project with database. There is a search by option (dropdown) to select by which attribute the user want to search and very next to dropdown their is a textfield where user can enter value and then click search. now i want to search for that particular value in that particular column(which is selected by user through the dropdowm) if it is exits i want to print them "found" if not then i want to display not found message.. Please find the attached images & code below.

For example: from dropdown if user select 'customer id' which is a column name and they enter id in the textfiled as '123456' then if it is exits in the column then i need to print found message else i need to print not found.

String column = jcombo2.getSelectedItem().toString();
    String value = key.getText();
    DefaultTableModel model = (DefaultTableModel) customerinfo.getModel();
    DefaultTableModel model2 = (DefaultTableModel) customerinfo.getModel();

    try {
     Connection con = (Connection) DriverManager.getConnection("jdbc:mysql://localhost/customerinfo", "root", "");
     Statement st = con.createStatement();
     ResultSet rs;
     String mysqlQuery = "SELECT * FROM `cust_info` WHERE `"+column+"` ='"+value+"'";
     rs =st.executeQuery(mysqlQuery);
     while(rs.next()) {
         String ci = rs.getString("customer id");
         model.addRow(new Object[] {ci});
     }


 }catch(Exception e) {
     System.out.println(e.getMessage());
 }

Answer 1

Try this:

String mysqlQuery = "SELECT COUNT(*) FROM `cust_info` WHERE `"+column+"` ='"+value+"'";
rs = st.executeQuery(mysqlQuery);
if (rs.next() && (rs.getInt(1) != 0))
  printFoundIt(); // or whatever you want to do
else
  printDidntFindIt(); // or whatever you want to do
st.close();

Or in case you want to fill the table with found items contemporarily:

String mysqlQuery = "SELECT * FROM `cust_info` WHERE `"+column+"` ='"+value+"'";
rs = st.executeQuery(mysqlQuery);
boolean found_it = false;
while (rs.next())
{
  found_it = true;
  String ci = rs.getString("customer id");
  model.addRow(new Object[] {ci});
}
st.close();

if (found_it)
  printFoundIt(); // or whatever you want to do
else
  printDidntFindIt(); // or whatever you want to do

Same as before but printing the 'found it' directly after having found the first element:

String mysqlQuery = "SELECT * FROM `cust_info` WHERE `"+column+"` ='"+value+"'";
rs = st.executeQuery(mysqlQuery);
boolean found_it = false;
while (rs.next())
{
  if (!found_it)
  {
    printFoundIt(); // or whatever you want to do
    found_it = true;
  }
  String ci = rs.getString("customer id");
  model.addRow(new Object[] {ci});
}
st.close();

if (!found_it)
  printDidntFindIt(); // or whatever you want to do