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mysql - 在 MySQL 中使用 ROLLUP 时将小数列四舍五入

问题描述

尝试在 MySQL 中使用 ROLLUP 时遇到问题。

我有一个这样创建的表。

create table order_items (
  id int,
  project_name varchar(50),
  order_date date,
  name varchar(20),
  unit_cost decimal(15,3),
  quantity decimal(15,3)
);

并像这样插入数据

insert into order_items (
  id, project_name, order_date, name, unit_cost, quantity
) values (
  1, "project 1", "2021-02-03", "order 1", 229.432, 14.599
);
insert into order_items (
  id, project_name, order_date, name, unit_cost, quantity
) values (
  2, "project 1", "2021-02-04", "order 2", 229.634, 15
);
insert into order_items (
  id, project_name, order_date, name, unit_cost, quantity
) values (
  3, "project 2", "2021-02-04", "order 3", 229.888, 15.543
);
insert into order_items (
  id, project_name, order_date, name, unit_cost, quantity
) values (
  4, "project 1", "2021-02-05", "order 4", 230.543, 1.5
);
insert into order_items (
  id, project_name, order_date, name, unit_cost, quantity
) values (
  5, "project 1", "2021-02-05", "order 5", 229.443, 1.5
);
insert into order_items (
  id, project_name, order_date, name, unit_cost, quantity
) values (
  6, "project 1", "2021-02-03", "order 1", 229.456, 18.234
);

我想按项目汇总每个日期的数量 = unit_cost * 数量，因此我将此查询与 一起使用ROLLUP，但 unit_cost 和数量列在结果表中四舍五入。（例如，第一行的 unit_cost 应该是 229.432 但它返回 229）

mysql> select order_date, project_name, name, unit_cost, quantity, sum(unit_cost * quantity) as amount from order_items group by order_date, project_name, name, unit_cost, quantity with rollup;
+------------+--------------+---------+-----------+----------+--------------+
| order_date | project_name | name    | unit_cost | quantity | amount       |
+------------+--------------+---------+-----------+----------+--------------+
| 2021-02-03 | project 1    | order 1 |       229 |       15 |  3349.477768 |
| 2021-02-03 | project 1    | order 1 |       229 |     NULL |  3349.477768 |
| 2021-02-03 | project 1    | order 1 |       229 |       18 |  4183.900704 |
| 2021-02-03 | project 1    | order 1 |       229 |     NULL |  4183.900704 |
| 2021-02-03 | project 1    | order 1 |      NULL |     NULL |  7533.378472 |
| 2021-02-03 | project 1    | NULL    |      NULL |     NULL |  7533.378472 |
| 2021-02-03 | NULL         | NULL    |      NULL |     NULL |  7533.378472 |
...
+------------+--------------+---------+-----------+----------+--------------+
25 rows in set (0.00 sec)

如果我删除ROLLUP， unit_cost 和 quantity 会返回到准确的值。

mysql> select order_date, project_name, name, unit_cost, quantity, sum(unit_cost * quantity) as amount from order_items group by order_date, project_name, name, unit_cost, quantity;
+------------+--------------+---------+-----------+----------+-------------+
| order_date | project_name | name    | unit_cost | quantity | amount      |
+------------+--------------+---------+-----------+----------+-------------+
| 2021-02-03 | project 1    | order 1 |   229.432 |   14.599 | 3349.477768 |
| 2021-02-04 | project 1    | order 2 |   229.634 |   15.000 | 3444.510000 |
| 2021-02-04 | project 2    | order 3 |   229.888 |   15.543 | 3573.149184 |
| 2021-02-05 | project 1    | order 4 |   230.543 |    1.500 |  345.814500 |
| 2021-02-05 | project 1    | order 5 |   229.443 |    1.500 |  344.164500 |
| 2021-02-03 | project 1    | order 1 |   229.456 |   18.234 | 4183.900704 |
+------------+--------------+---------+-----------+----------+-------------+
6 rows in set (0.00 sec)

有什么方法可以使用ROLLUP但保持对十进制类型的列进行分组的准确值？

MySQL 版本是 8.0.21。

标签： mysqlrollup

解决方案

尝试了8.0.20、8.0.22、8.0.23版本后，发现这个问题是8.0.21版本引入的bug，在8.0.23已经修复。

https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-23.html

添加 WITH ROLLUP 时，某些正确执行的 group by 查询未返回预期结果。这是因为十进制信息并不总是正确地通过汇总组项目传输，导致返回十进制值的函数（例如 TRUNCATE()）接收错误类型的数据。（错误 #101684、错误 #32179240）

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