Question

我有以下的peewee表/类（在postgres DB上）和虚线下面的一个我喜欢的例子。

基本上我是在数据库查询中完成newb并且不知道如何构建它：我需要，给出一个日期列表（例如[＆＃39; 2015-01-01＆＃39;，... ]）获取每天警报的数量（如果有的话）作为每个服务的计数。希望下面的例子足够清楚。

class Event(BaseModel):
    assessment = CharField(max_length = 4096)
    day = DateField()
    ongoing = BooleanField()
    alertType = CharField(null = True)
    links = CharField(null = True, max_length = 4096)
    newLinks = CharField(null = True, max_length = 4096)
    startTime = TimeField()
    endTime = TimeField(null = True)

class Service(BaseModel):
    svcid = TextField(unique = True)
    name = TextField()

class Alert(BaseModel):
    alertId = CharField(unique = True, null = True)
    alertLink = CharField(unique = True, null = True)
    startTime = TimeField()
    endTime = TimeField(null = True)
    jcaLink = CharField(max_length = 4096, null = True)
    description = CharField(max_length = 4096)
    relatedNodes = CharField(null = True)
    customerName = CharField(null = True)
    jcaUrl = CharField(null = True)
    deviceName = CharField(null = True)
    event = ForeignKeyField(Event, related_name = 'alerts')
    service = ForeignKeyField(Service, related_name = 'alerts')
    hosted = CharField(default = None, null = True)

------------------------------------------------------------

Example: Event.id 1 has Event.day '2015-01-01'
         Event.id 2 has Event.day '2015-01-02'
         Service.id 1 has name "A"
         Service.id 2 has name "B"
         Alert.id 1 has Alert.event.id 1, Alert.service.id 1
         Alert.id 2 has Alert.event.id 2, Alert.service.id 2
         Alert.id 3 has Alert.event.id 2, Alert.service.id 1
         # end of db

If days is ['2015-01-01', '2015-01-02'], output should be like (not resembling, just broken up/organized somewhat like)
Service A
day 2015-01-01 
1 alert
day 2015-01-02
1 alert
-----------------
Service B
day 2015-01-01
1 alert
day 2015-01-02
0 alerts

Answer 1

这应该这样做。我不确定你的模型是否添加了像s.id这样的列，但我想它确实如此。你的start_time是一个时间字段，所以我使用date()方法，所以我们只是比较日期部分。

select s.name, date(a.start_time) as alert_date, count(s.name) as alerts
from alert a join service s on a.service_id = s.id
where date(a.start_time) in ('2015-01-01', '2015-01-02')
group by s.name, alert_date

请注意，在执行分组时，所有选定的字段必须在group by或aggregate函数中使用。有办法解决这个问题，但由于你需要这么少的数据，所以我不认为service.name是唯一的。

此外，如果您希望按月，年等方式收到提醒，则可以使用extract，如下所示：

select s.name, extract(month from a.start_time) as alert_month, 
extract(year from a.start_time) as alert_year, count(s.name) as alerts
from alert a join service s on a.service_id = s.id
where extract(year from a.start_time) = 2015
and extract(month from a.start_time) in (11, 12)
group by s.name, alert_month, alert_year

peewee orm：用外键加入三个表，计算中间表

1 个答案: