Question

如果提供的值存在，我想获取PK记录。如果不是我想插入提供的值并获得自动递增的主键。我做的是：

 String sql= "SELECT id FROM markets where market = 'value';";
 ResultSet rs=executeQuery(sql);
 int id;
 if (!rs.isBeforeFirst() ) {    
      //there is No record found. must be created
         rs.close();
         conn = DriverManager.getConnection(DB_URL,USER,PASS);
         st = conn.createStatement();
         String query = "INSERT INTO markets (market) VALUES('value')";
         st.executeUpdate(query);
//       created now we want the ID of the new market
         rs=executeQuery(sql);
         id =rs.getInt("id");
         System.out.println("ID"+id);
          rs.close();
     } 
     else
       while (rs.next()){
          //the value exist, we get the ID of it
          id =rs.getInt("id");
          System.out.println(".."+id);
       }

和方法executeQuery定义：

public static ResultSet executeQuery(String query){
        Connection conn = null;
        Statement stmt = null;      
          try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(DB_URL,USER,PASS);
            stmt = conn.createStatement();
            String sql;         
            return  stmt.executeQuery(query);           
          } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

这是正确的方法吗？

如果是，为什么我会得到一个java.sql.SQLException：在开始结果集之前在

//  created now we want the ID of the new market
rs=executeQuery(sql);
id =rs.getInt("id");//<<<<-----Exception Here
System.out.println("ID"+id);

在插入之前和之后执行两次相同的查询

0 个答案: