Question

有没有办法检查几行中某个列值是否相同？

我需要检查客户是否在我的数据库中放置了多个订单。

如果我选择

SELECT * FROM orders WHERE email = 'customer@email.com'

这可能会产生

OrderID   Product   Amount   email
50        Apples    1        customer@email.com 
50        Oranges   1        customer@email.com
50        Bananas   1        customer@email.com
91        Apples    1        customer@email.com

所以我需要检查这些行中的OrderID是否相同。

但是怎么样？

Answer 1

使用count（）函数和group by子句来警告订单ID包含的记录数：

select email, orderid, count(*) as number_orders_per_orderid
from orders
where email = 'customer@email.com'
group by email, orderid

或者，如果您想计算用户订单的数量，请使用count（distinct ...）和group by：

select email, count(distinct orderid) as number_of_orders
from orders
where email = 'customer@email.com'
group by email

Answer 2

您可以使用分组和

select id, count(*) from orders group by id 
WHERE email = 'customer@email.com'
having count(*) > 1

Answer 3

你可以得到一个＆＃34;只有一个＆＃34;如果客户有一个ORDERID 如果客户使用CASE ... WHEN具有多个ORDERID

，您可以获得多个＆＃34;多个＆＃34;

这是一个例子

SELECT email,COUNT(*) as number_order ,
(CASE WHEN count(*)=1 THEN "Just one" WHEN count(*)>1 THEN "More than one" END) AS number_order_status
FROM orders  GROUP BY email

Mysql - 检查多行的特定列是否相同

3 个答案: