如何在子查询中求和然后分组？答案

【问题标题】：How do I sum then group by in a subquery?如何在子查询中求和然后分组？
【发布时间】：2021-09-16 08:51:44
【问题描述】：

我有以下

SELECT
ticketNum, 
name,
id,
created

打印出来的

ticketNum	name	id	created
abc	andy	1	2021-07-02 10:58:54.476 UTC
abc	bob	1	2021-07-02 10:58:54.476 UTC
abc	andy	1	2021-07-02 10:58:54.476 UTC
abc	charlie	1	2021-07-02 10:58:54.476 UTC

我想返回每个人和每一天的ticketNum总和所以想要的结果：

Name	Sum of TicketNum	Date
andy	2	2021-07-02
bob	1	2021-07-02
charlie	1	2021-07-02

我想我可能会从以下内容开始，但我认为我的理解不正确。

SELECT 
name,
(SELECT
    COUNT(DISTINCT ticketNum)
    FROM mytable
    WHERE name = name
)

【问题讨论】：

提示：GROUP BY。你试过吗？

标签： sql group-by count subquery

【解决方案1】：

你可以试试

架构 (MySQL v8.0)

CREATE TABLE my_table (
  `ticketNum` VARCHAR(3),
  `name` VARCHAR(7),
  `id` INTEGER,
  `created` DATETIME
);

INSERT INTO my_table
  (`ticketNum`, `name`, `id`, `created`)
VALUES
  ('abc', 'andy', '1', '2021-07-02 10:58:54.476'),
  ('abc', 'bob', '1', '2021-07-02 10:58:54.476'),
  ('abc', 'andy', '1', '2021-07-02 10:58:54.476'),
  ('abc', 'charlie', '1', '2021-07-02 10:58:54.476');

查询 #1

SELECT
    name Name,
    COUNT(ticketNum) 'Sum of TicketNum',
    MAX(created) as Date
FROM
    my_table
GROUP BY
    name;

Name	Sum of TicketNum	Date
andy	2	2021-07-02 10:58:54
bob	1	2021-07-02 10:58:54
charlie	1	2021-07-02 10:58:54

View on DB Fiddle

【讨论】：