what will rs.getString(1) return if the SQL query returns nothing

Question

heres my code :

code for connecting database :

Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection con=DriverManager.getConnection("jdbc:sqlserver://localhost:1433;databaseName=city_mart;user=sa;password=aptech");
Statement st=con.createStatement();

String sql="Select Emp_login_ID from employee where Emp_login_ID = '"+r3.getText()+"' ";
ResultSet rs=st.executeQuery(sql);

String login = rs.getString(1);

if (r3.getText().equalsIgnoreCase(login))
{
    JOptionPane.showMessageDialog(rootPane, "Login ID not available.");
}
else
{
    JOptionPane.showMessageDialog(rootPane, "Login ID is available.");
}

thanks.any help is much appreciated.

The Class.forName() line has been unnecessary since about 2007. — user207421, Jul 17 '14 at 02:58

score 2 · Answer 1 · edited May 23 '17 at 12:13

You have forgotten to call ResultSet#next() before calling ResultSet#getString()

First move the cursor at the the first row then get value of any column.

I suggest you to use PreparedStatment instead of Statement.

Read tutorial on Using Prepared Statements and When we use PreparedStatement instead of Statement?

It should be like this: (check the value returned by rs.next())

String sql="Select Emp_login_ID from employee where Emp_login_ID = ?";
PreparedStatement st = con.prepareStatement(sql);
st.setString(1,r3.getText());

ResultSet rs=st.executeQuery(sql);
if(rs.next()){
     String login = rs.getString(1);
     JOptionPane.showMessageDialog(rootPane, "Login ID is available.");
}else{
     JOptionPane.showMessageDialog(rootPane, "Login ID not available.");
}

score 0 · Answer 2 · answered Jul 17 '14 at 02:03

You can try :

Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection con=DriverManager.getConnection("jdbc:sqlserver://localhost:1433;databaseName=city_mart;user=sa;password=aptech");
Statement st=con.createStatement();

String sql="Select Emp_login_ID from employee where Emp_login_ID = '"+r3.getText()+"' ";
ResultSet rs=st.executeQuery(sql);


while(rs.next()){
  String login = rs.getString(1);
  if (r3.getText().equalsIgnoreCase(login))
   {
    JOptionPane.showMessageDialog(rootPane, "Login ID not available.");
   }
   else
   {
    JOptionPane.showMessageDialog(rootPane, "Login ID is available.");
   }
}

Moves the cursor froward one row from its current position. A ResultSet cursor is initially positioned before the first row; the first call to the method next makes the first row the current row; the second call makes the second row the current row, and so on.

You can read about Next method of Result Set here

Not a good way to use single quotes in query. It's not supported by all databases. — Braj, Jul 17 '14 at 02:20
read [When we use PreparedStatement instead of Statement?](http://stackoverflow.com/questions/2099425/when-we-use-preparedstatement-instead-of-statement) — Braj, Jul 17 '14 at 02:21

score 0 · Answer 3 · answered Jul 17 '14 at 02:15

0

It will throw an exception because you have failed to call ResultSet.next(). If you had called it, it would have returned false, and you shouldn't have called rs.getString() at all.

answered Jul 17 '14 at 02:15

user207421

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what will rs.getString(1) return if the SQL query returns nothing

3 Answers3