在SQL查询中使用组合框的值

Question

How can I use the value of a combo box in a SQL query with Java? I try this code but it doesn't work.

String sql = " select * from table1 where ? like ?";
    try{
        pst = conn.prepareStatement(sql);
        pst.setString(1, (String) jComboBox2.getSelectedItem());
        pst.setString(2, txtsearch.getText() + "%");
        rs = pst.executeQuery();}

If I use this code, it works.

String sql = " select * from table1 where Name like ?";
    try{
        pst = conn.prepareStatement(sql);
        pst.setString(1, txtsearch.getText() + "%");
        rs = pst.executeQuery();}

Answer 1

Well, you can do something like this:

try {
    String sql = "select * from table1 where ";
    sql += (String) jComboBox2.getSelectedItem();
    sql += " like ";
    sql += txtsearch.getText() + "%";
    pst = conn.prepareStatement(sql);
    rs = pst.executeQuery();
}

Answer 2

The place holder (?) is actually designed for the column values not for column/table name. Make use of string concatenation:

String sql = "select * from table1 where "
                                  + jComboBox2.getSelectedItem()
                                  +" like ?";