ResultSet 循环少于行数答案

【问题标题】：ResultSet looping less than number of rowsResultSet 循环少于行数
【发布时间】：2013-07-03 11:56:34
【问题描述】：

我有一个返回 50 行的 ResultSet。我需要有一个临时表，我可以在其中插入这 50 行，以便我可以对其执行查询。

没有其他选择，所以请不要建议使用子查询或其他东西。需要一个临时表。

所以我使用以下方法插入行，显然虽然我知道 ResultSet 包含 50 行，但它在 while 循环中仅循环 13 次，因此当我从该表中提取一些字段时，我没有所需的结果。

public void insertValues(Connection con, ResultSet rs) {

    StringBuffer insert_into_temp = new StringBuffer();

    try {
        ResultSetMetaData rsmd = rs.getMetaData();
        int colCount = rsmd.getColumnCount();


        insert_into_temp.append("INSERT INTO SESSION.RETURNED_TICKETS (");

        for (int i = 1; i <= colCount; i++) {
            insert_into_temp.append(rsmd.getColumnLabel(i)); 
            insert_into_temp.append(",");
        }

        insert_into_temp.deleteCharAt(insert_into_temp.length()-1);
        insert_into_temp.append(")");

        insert_into_temp.append("\nVALUES(");

        // number of place-holders for values
        for (int i = 0; i < colCount; i++) {
             insert_into_temp.append("?,");  
        }

        insert_into_temp.deleteCharAt(insert_into_temp.length()-1);
        insert_into_temp.append(")");

        while(rs.next()){
            PreparedStatement pstmt = con.prepareStatement(insert_into_temp.toString());

            pstmt.setInt(1, rs.getInt(Ticket.FLD_ID));
            pstmt.setString(2, rs.getString(Ticket.FLD_DESCRIPTION));
            pstmt.setInt(3, rs.getInt(Ticket.FLD_TICKETTYPE));
            pstmt.setString(4, rs.getString("STATE"));
            pstmt.setString(5, rs.getString("PRIORITY"));
            pstmt.setString(6, rs.getString("OWNER"));
            pstmt.setString(7, rs.getString("SUBMITTER"));
            pstmt.setString(8, rs.getString("TYPE"));
            pstmt.setString(9, rs.getString(Ticket.FLD_TITLE));
            pstmt.setString(10, rs.getString("PROJECT"));
            pstmt.setInt(11, rs.getInt("PROJID"));
            pstmt.setDouble(12, rs.getDouble("RELEASE"));
            pstmt.setTimestamp(13, rs.getTimestamp(Ticket.FLD_SUBMITDATE));
            pstmt.setInt(14, rs.getInt(Ticket.FLD_CUSTOMER));  
            pstmt.setInt(15, rs.getInt("ROW_NEXT")); 

            int success = pstmt.executeUpdate();

            if (success != 1) // if not successful
                throw new SQLException("Failed to insert values into temporary table for linked/unlinked tickets");

        }

    } catch (SQLException e){
        LogFile.logError("[Report.execute()] "+e.getMessage());
        LogFile.logError(insert_into_temp.toString());
    }
}

可能是什么问题？我无法弄清楚为什么会这样。谢谢

【问题讨论】：

@Bernice..t 表示您需要临时表？
您可以通过删除所有这些插入代码来缩小您的问题范围。只需从结果集中打印出来。
是的，我正在插入临时表。但正是这个 while 循环只循环了 13 次，并且只插入了 13 行，所以我认为这是相关的代码。打印输出只是从 where id in statement 中选择
在处理 SELECT 语句结果的循环内使用 INSERT 效率极低。整个循环可以用 single 语句替换为 insert into ... select ... 行，这将更加更有效率。
@beny23：即使使用批处理语句，最有效的方法是在没有任何循环的单个语句中执行此操作

标签： java sql resultset

【解决方案1】：

如果我正确理解问题，而不是像这样每次使用都执行查询，

con.setAutoCommit(false); while (rs.next()) { // your setting values on prepared statement code pstmt.addBatch(); } pstmt.executeBatch(); con.setAutoCommit(true);

【讨论】：

【解决方案2】：

这并不能回答您的问题，但它确实说明了如何避免为每次迭代创建准备好的语句。相反，您可以准备一次，然后在每次迭代中绑定不同的值。

public void insertValues(Connection con, ResultSet rs) {
    try {

        StringBuffer insert_into_temp = new StringBuffer();

        ResultSetMetaData rsmd = rs.getMetaData();
        int colCount = rsmd.getColumnCount();

        insert_into_temp.append("INSERT INTO SESSION.RETURNED_TICKETS (");

        for (int i = 1; i <= colCount; i++) {
            insert_into_temp.append(rsmd.getColumnLabel(i)); 
            insert_into_temp.append(",");
        }

        insert_into_temp.deleteCharAt(insert_into_temp.length()-1);
        insert_into_temp.append(")");

        insert_into_temp.append("\nVALUES(");

        // number of place-holders for values
        for (int i = 0; i < colCount; i++) {
             insert_into_temp.append("?,");  
        }
        insert_into_temp.deleteCharAt(insert_into_temp.length()-1);
        insert_into_temp.append(")");

        PreparedStatement pstmt = con.prepareStatement(insert_into_temp.toString());

        while (rs.next()) {

            pstmt.setInt(1, rs.getInt(Ticket.FLD_ID));
            pstmt.setString(2, rs.getString(Ticket.FLD_DESCRIPTION));
            pstmt.setInt(3, rs.getInt(Ticket.FLD_TICKETTYPE));
            pstmt.setString(4, rs.getString("STATE"));
            pstmt.setString(5, rs.getString("PRIORITY"));
            pstmt.setString(6, rs.getString("OWNER"));
            pstmt.setString(7, rs.getString("SUBMITTER"));
            pstmt.setString(8, rs.getString("TYPE"));
            pstmt.setString(9, rs.getString(Ticket.FLD_TITLE));
            pstmt.setString(10, rs.getString("PROJECT"));
            pstmt.setInt(11, rs.getInt("PROJID"));
            pstmt.setDouble(12, rs.getDouble("RELEASE"));
            pstmt.setTimestamp(13, rs.getTimestamp(Ticket.FLD_SUBMITDATE));
            pstmt.setInt(14, rs.getInt(Ticket.FLD_CUSTOMER));  
            pstmt.setInt(15, rs.getInt("ROW_NEXT")); 

            int success = pstmt.executeUpdate();

            if (success != 1) // if not successful
                throw new SQLException("Failed to insert values into temporary table for linked/unlinked tickets");

        }

    } catch (SQLException e){
        LogFile.logError("[Report.execute()] "+e.getMessage());
        LogFile.logError(insert_into_temp.toString());
    }
}

【讨论】：