sql - T-sql每天获取最小值和最大值

Question

我正在尝试编写一个查询，每天从价格明细表中获取每件商品的最低和最高价格。

在价格明细表中，价格一天设置多次，因此同一日期有很多记录。所以我想要一个表，其中每个日期都有一行，然后将该表连接到同一个表，因此对于每个不同的日期，我想要最小值和最大值。

USE [a_trading_system]
GO

/****** Object:  Table [dbo].[price_details]    Script Date: 07/01/2012 17:28:31 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[price_details](
    [price_id] [int] IDENTITY(1,1) NOT NULL,
    [exch_ticker] [varchar](8) NOT NULL,
    [price_set_date] [datetime] NOT NULL,
    [buy_price] [decimal](7, 2) NOT NULL,
    [sell_price] [decimal](7, 2) NOT NULL,
 CONSTRAINT [PK_price_detail] PRIMARY KEY CLUSTERED 
(
    [price_id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF,   ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[price_details]  WITH CHECK ADD  CONSTRAINT    [FK_price_details_Contract] FOREIGN KEY([exch_ticker])
REFERENCES [dbo].[Contract] ([exch_ticker])
GO

ALTER TABLE [dbo].[price_details] CHECK CONSTRAINT [FK_price_details_Contract]
GO

SQL 查询

select distinct 
substring(convert(varchar(12),p1.price_set_date), 0, 12),
p2.exch_ticker,
(select MIN(buy_price) from price_details ),
(select MAX(buy_price) from price_details )
from price_details as p1

left join price_details as p2 on p2.exch_ticker = p1.exch_ticker 

where p1.exch_ticker = p2.exch_ticker

group by p1.price_set_date, p2.exch_ticker

总结

表中有许多价格是在同一天设定的。想要每个交易所代码每天的最小值和最大值。

谢谢

Answer 1

一个简单的 group by 应该可以工作:

select  cast(price_set_date as date) as [Date]
,       exch_ticker 
,       min(buy_price) as MinPrice
,       max(buy_price) as MaxPrice
from    price_details as p
group by 
        exch_ticker
,       cast(price_set_date as date)

不确定您的示例查询为何使用自联接。如果有充分的理由，请为您的问题添加解释。