Question

JAVA SUM SQL语句怎么拼 带动态传参的 一直报错

public String WaresCollect(String str){
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
String number = null;
try {
//获得链接对象
connection = CiteUtil.getConnection();
//针对商品信息表聚合查询拼写SQL语句
String sql = "select SUM ? from SPMXTable";
//将SQL语句发送数据库获得语句对象
preparedStatement = connection.prepareStatement(sql);
//通过语句对象实现动态传参数
preparedStatement.setString(1,"("+str+")");
//返回结果集
resultSet = preparedStatement.executeQuery();
//拿到总和结果值
while(resultSet.next()){
number = resultSet.getString(1);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}finally{
CiteUtil.closeAllSource(connection, preparedStatement, resultSet);
}
return number;
}
这是我代码说什么字符串不能用聚合函数 在数据库里面不是可以带列名么！求助！

Answer 1

select sum(字段) from biao