Question

我正在尝试创建一个select count语句，其中where语句对于每一行都不同例如，我得到了下表dbo.job：

User:    Job:
Mark     Garbageman
Dirk     Garbageman
Henk     Garbageman
Steven   Garbageman
Mark     Delivery
Dirk     Delivery
Henk     Delivery
Steven   Delivery
Stevens  Delivery

现在我想知道我在垃圾箱的工作中有多少用户“工作”，为此我使用：

Select COUNT(user) as count from job WHERE job.job = 'Garbageman'

我会得到以下结果：

Count:
4

现在我也想知道有多少用户在同一个选择语句中完成了交付工作，我会得到类似的信息：

Select COUNT(user) as GarbageCount, COUNT(user) as Deliverycount from job WHERE job.job = 'Garbageman'

现在我将得到以下结果：

GarbageCount:   DelivryCount:
4               4

但我想：

现在我将得到以下结果：

GarbageCount:   DelivryCount:
4               5

我知道为什么我的陈述失败了，那是因为我只使用1 where语句。但是GarbageCount和DeliveryCount的where语句是不同的。我根本不知道如何创建这样的查询。

有人有什么建议吗？

Answer 1

你可以使用Case When with Count。

http://peoplesoft.wikidot.com/conditional-counting-in-sql
MSDN参考 - ＆gt; http://msdn.microsoft.com/en-us/library/ms175997.aspx

select
    count(case when Job = 'Garbageman' then 1 end) as GarbageCount,
    count(case when Job = 'Delivery' then 1 end) as DeliveryCount
from Job

Answer 2

您可以使用条件sum()

来实现此目的

select
sum(Job = 'Garbageman') as GarbageCount,
sum(Job = 'Delivery') as DelivryCount
from job

Answer 3

您可以使用条件聚合。 ANSI标准方法是：

Select sum(case when j.job = 'Garbageman' then 1 else 0 end) as GarbageCount,
       sum(case when j.job = 'Delivery' then 1 else 0 end) as Deliverycount
from job j;

您没有指定数据库，但MySQL也提供了以下快捷方式：

Select sum(j.job = 'Garbageman') as GarbageCount,
       sum(j.job = 'Delivery') as Deliverycount
from job j;

Sql Select语句具有不同的where语句

3 个答案: