3

我有一张桌子，里面ga_sum_1有一列created_timestamp。当我从 mysql 命令行执行以下查询时：

mysql> select max(created_timestamp) from ga_sum_1;
+------------------------+
| max(created_timestamp) |
+------------------------+
| 2017-11-05 00:59:55    |
+------------------------+
1 row in set (0.00 sec)

如果我从一个非常简单的存储过程中做同样的事情：

delimiter //
create procedure test()
begin
  select max(created_timestamp) from ga_sum_1;
end//
delimiter ;

mysql> call test();
+------------------------+
| max(created_timestamp) |
+------------------------+
| 2017-11-05 00:59:55    |
+------------------------+
1 row in set (0.00 sec)

但是，当我在存储过程中这样做时：

drop procedure if exists test;

delimiter //

create procedure test()
begin
  declare cursor_end condition for sqlstate '02000';
  declare finished int default 0;
  declare game_id int(11);
  declare user_id int(11);
  declare game_instance_id bigint(20);
  declare currency varchar(15);
  declare created_timestamp timestamp;
  declare wager decimal(18,2);
  declare win decimal(18,2);
  -- cursor
  declare game_action_csr cursor for select * from game_action_view;
  declare continue handler for cursor_end set finished=1;

  -- create view dynamically
select max(created_timestamp) from ga_sum_1;

end//

delimiter ;

mysql> call test();
+------------------------+
| max(created_timestamp) |
+------------------------+
| NULL                   |
+------------------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

在最后一个例子中我做错了什么？

====编辑====

一些进一步的研究表明，它是declare created_timestamp- 显然混淆了同名列上的选择！

4

2 回答 2

4

这可能是因为这条线：

  declare created_timestamp timestamp;
于 2019-09-23T14:23:02.740 回答
3

作为另一个答案的替代方案，您可以更具体：

select max(ga_sum_1.created_timestamp) from ga_sum_1
于 2019-09-23T14:33:15.470 回答