记一个简单的sql查询

Posted 2020-06-29 Catcher Wong

一个简单的sql查询

在我们做各类统计和各类报表的时候，会有各种各样的查询要求、条件

这篇主要记录一个常见的统计查询

要求如下：

统计一段时间内，每天注册人数，如果某天没有人注册则显示为0

现在建个简单的表来试试

建表语句如下：

 1 CREATE TABLE [dbo].[UserInfo](
 2     [UserID] [int] IDENTITY(1,1) NOT NULL,
 3     [UserName] [varchar](50) NOT NULL,
 4     [URegTime] [datetime] NOT NULL,
 5  CONSTRAINT [PK_UserInfo] PRIMARY KEY CLUSTERED 
 6 (
 7     [UserID] ASC
 8 )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
 9 ) ON [PRIMARY]
10 GO

 

然后向其插入一些数据

 1 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher1\',\'2016-03-01 8:00:00\')
 2 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher2\',\'2016-03-01 9:00:00\')
 3 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher3\',\'2016-03-05 8:00:00\')
 4 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher4\',\'2016-03-05 20:00:00\')
 5 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher5\',\'2016-03-07 8:00:00\')
 6 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher6\',\'2016-03-09 8:00:00\')
 7 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher7\',\'2016-03-11 8:00:00\')
 8 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher8\',\'2016-03-11 18:00:00\')
 9 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher9\',\'2016-03-15 8:00:00\')
10 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher10\',\'2016-03-17 8:00:00\')
11 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher11\',\'2016-03-17 11:00:00\')
12 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher12\',\'2016-03-17 13:00:00\')
13 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher13\',\'2016-03-18 8:00:00\')
14 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher14\',\'2016-03-19 8:00:00\')
15 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher15\',\'2016-03-20 8:00:00\')
16 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher16\',\'2016-03-20 11:00:00\')
17 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher17\',\'2016-03-20 12:00:00\')
18 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher18\',\'2016-03-21 8:00:00\')
19 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher19\',\'2016-03-21 9:00:00\')
20 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher20\',\'2016-03-22 8:00:00\')
21 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher21\',\'2016-03-22 12:00:00\')
22 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher22\',\'2016-03-26 8:00:00\')
23 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher23\',\'2016-03-26 10:00:00\')
24 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher24\',\'2016-03-26 11:00:00\')
25 INSERT INTO [dbo].[UserInfo]([UserName],[URegTime])VALUES(\'catcher25\',\'2016-03-26 20:00:00\')

 

下面来看看编写符合要求的sql查询

 1 select b.regTime,userCount =isnull(a.userCount,0)
 2 from
 3 (
 4 select regTime=convert(varchar(10),dateadd(dd,number,\'2016-03-01\'),120)
 5 from master..spt_values
 6 where type=\'p\'  and number <= datediff(dd,\'2016-03-01\',GETDATE())
 7 ) b
 8 left join 
 9 (
10 select 
11 userCount = COUNT(*),
12 regTime = CONVERT(varchar(4),YEAR(u.URegTime))+\'-\' +right(cast(month(u.URegTime)+100 as varchar),2) +\'-\'+right(cast(Day(u.URegTime)+100 as varchar),2) 
13 from UserInfo u
14 group by YEAR(u.URegTime),Month(u.URegTime),Day(u.URegTime)
15 ) a  on a.regTime  = b.regTime

来看看结果，左边是原始数据，右边是统计数据

        

 

思路很简单，找出这段时间范围内(2016年3月1号到今天)的所有日期去跟我们相应的数据进行左连接即可！

 

其中用到了一个系统常量表 master..spt_values

 

一些相关这个表的具体内容可以看看下面的文章

Master..spt_values system table

SQLServer——MASTER..spt_values

SQL Server 中master..spt_values的应用