Question

我有一个MySQL表

discount_vouchers
------------------
id
email
test_id

我的目标是列出使用给定电子邮件和GROUP BY中给定的test_id多次出现的所有优惠券：

GROUP BY email, test_id
HAVING count(*) >1

如何阅读此群组？

以下是一个例子：

discount_vouchers
------------------
1    1@test.com    20
2    1@test.com    10
3    1@test.com    20
4    2@test.com    30

我希望得到结果：

id     email     test_id   count
1    1@test.com    20       2
2    1@test.com    10       1
3    1@test.com    20       2
4    2@test.com    30       2

Answer 1

尝试类似以下内容

SELECT C2, counter from 
(SELECT C2, COUNT(*) as counter FROM test.mytable
GROUP BY C2) as aggregation
WHERE counter > 1

如果不使用group by，您可以执行类似

的操作

SELECT a.* , 
   (SELECT count(*) FROM discount_vouchers b 
    WHERE a.email = b.email AND a.test_id = b.test_id) as count
FROM discount_vouchers a

Answer 2

这个怎么样？使用子查询聚合，并使用其结果以丰富实际表：

SELECT `discount_vouchers`.*, `counts`.`count`
FROM   `discount_vouchers`
       INNER JOIN (SELECT `email`, `test_id`, Count(*) AS 'count' 
                   FROM   `discount_vouchers`) AS `counts` 
           ON `discount_vouchers`.`email` = `counts`.`email`
          AND `discount_vouchers`.`test_id` = `counts`.`test_id`;

MYSQL - 没有group by的count（*）

2 个答案: