Question

这是我的sql

select count(type), type
from tasks
group by type

这里有4行。

count(type) type
8           Trial
7           New
3           Service
4           Uninstall

如何在一行中获得结果

Trial   New Service Uninstall
8       7   3       4

我知道必须自己加入桌子。但我无法准确得到。

以下是样本表数据

id  type        date
1   New         2017-10-07
2   Trial       2017-10-01
3   New         2017-10-02
4   Uninstall   2017-10-05
5   Trial       2017-10-06
6   Trial       2017-10-07

Answer 1

SELECT MAX(CASE WHEN type = 'Trial' THEN count_type END) as Trial,
       MAX(CASE WHEN type = 'New' THEN count_type END) as New,
       MAX(CASE WHEN type = 'Service' THEN count_type END) as Service,
       MAX(CASE WHEN type = 'Uninstall' THEN count_type END) as Uninstall
FROM (select count(type) as count_type , type
      from tasks
      group by type) T

Answer 2

这是通过条件聚合完成的：

SUM

在MySQL中，

true为1且false为0，因此我们可以使用from datetime import timedelta from django.db import migrations, models import django.utils.timezone # noinspection PyUnusedLocal def set_free_credits_added_on(apps, schema_editor): # noinspection PyPep8Naming UserProfile = apps.get_model('core', 'UserProfile') for user_profile in UserProfile.objects.all(): user_profile.free_credits_added_on = user_profile.next_billing - timedelta(days=30) user_profile.save() # noinspection PyUnusedLocal def do_nothing(apps, schema_editor): pass class Migration(migrations.Migration): dependencies = [ ('core', '0078_auto_20171104_0659'), ] operations = [ migrations.AddField( model_name='userprofile', name='free_credits_added_on', # This default value is overridden in the following data migration code field=models.DateTimeField( auto_now_add=True, default=django.utils.timezone.now, verbose_name='Free Credits Added On' ), preserve_default=False, ), migrations.RunPython(code=set_free_credits_added_on, reverse_code=do_nothing), ]来计算匹配。

我的小组按类型和计数自我加入表来获取摘要

2 个答案: