sql查询在eclipse中不起作用

Question

我有一个查询在SQLyog中运行良好，但不在eclipse中。我调试时显示的错误是“找不到列”。

这里是我的查询：

String searchQuery = "select AVG(Rating) from rating where CoursesID=? and MONTH(dtDate)=? group by dtDate"; 

表：

ID  | CoursesID | Rating | Comment | dtDate 

11111 | SKM3207 | 5  | No  | 2015-05-20 

的Java

//preparing some objects for connection 
     Connection currentCon = null; 
     ResultSet rs = null; 
     PreparedStatement pstmt = null; 
     //double totalRate = 0.0; 

     Vector<String> monthRating = new Vector<String>(); 

     try{ 
      String searchQuery = "select AVG(Rating) from rating where CoursesID=? and MONTH(dtDate)=? group by dtDate"; 

      //connect to DB 
      currentCon = ConnectionManager.getConnection(); 
      pstmt=currentCon.prepareStatement(searchQuery); 
      pstmt.setString(1, CoursesID); 
      pstmt.setString(2, fmonth); 
      rs = pstmt.executeQuery(); 

      while(rs.next()){ 
       monthRating.add(rs.getString("Rating")); 
       //String avg = rs.getString(1); 
       //totalRate = Double.parseDouble(avg); 
      } 
     } 

     catch (Exception ex){ 
      System.out.println("Log In failed: An Exception has occurred! " + ex); 
     } 

     //some exception handling 
     finally{ 
      if (rs != null) { 
       try { 
       rs.close(); 
       } catch (Exception e) {} 
       rs = null; 
       } 

      if (pstmt != null) { 
       try { 
       pstmt.close(); 
       } catch (Exception e) {} 
       pstmt = null; 
       } 

      if (currentCon != null) { 
       try { 
       currentCon.close(); 
       } catch (Exception e) { 
       } 

       currentCon = null; 
      } 
     } 

      return monthRating; 

是，任何需要添加到其中，因此它可以在Eclipse中运行？

Answer 1

您正在使用评级为rs.getString("Rating")而评级在SQL语句中没有别名，而在聚集中使用。只需添加一个别名

SELECT AVG(Rating) AS Rating .... 

Answer 2

在您的查询，你不为你检索列定义一个名字：

select AVG(Rating) from ... 

所以，当你执行这个：

rs.getString("Rating") 

你得到一个异常。查询更改为：

select AVG(Rating) AS Rating from ... 

Answer 3

monthRating.add(rs.getString("Rating")); 

您取出由resultSetRating列，但查询有AVG(Rating)为列名，以便将其更改为，

monthRating.add(rs.getString("AVG(Rating)");