15个初学者必看的基础SQL查询语句

译文链接：http://www.codeceo.com/article/15-basic-sql-for-beginner.html
英文原文：Basic SQL Queries for Beginners

1、创建表和数据插入SQL

我们在开始创建数据表和向表中插入演示数据之前，我想给大家解释一下实时数据表的设计理念，这样也许能帮助大家能更好的理解SQL查询。

在数据库设计中，有一条非常重要的规则就是要正确建立主键和外键的关系。

现在我们来创建几个餐厅订单管理的数据表，一共用到3张数据表，Item Master表、Order Master表和Order Detail表。

创建表：

创建Item Master表：

CREATE TABLE [dbo].[ItemMasters](

    [Item_Code] [varchar](20) NOT NULL,

    [Item_Name] [varchar](100) NOT NULL,

    [Price]  Int NOT NULL,

    [TAX1]  Int NOT NULL,

    [Discount]  Int NOT NULL,

    [Description] [varchar](200) NOT NULL,

    [IN_DATE] [datetime] NOT NULL,

    [IN_USR_ID] [varchar](20) NOT NULL,

    [UP_DATE] [datetime] NOT NULL,

    [UP_USR_ID] [varchar](20) NOT NULL,

 CONSTRAINT [PK_ItemMasters] PRIMARY KEY CLUSTERED 

(

    [Item_Code] ASC

)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]

) ON [PRIMARY]

向Item Master表插入数据：

INSERT INTO [ItemMasters]   ([Item_Code],[Item_Name],[Price],[TAX1],[Discount],[Description],[IN_DATE]

           ,[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('Item001','Coke',55,1,0,'Coke which need to be cold',GETDATE(),'SHANU'

           ,GETDATE(),'SHANU')



INSERT INTO [ItemMasters]   ([Item_Code],[Item_Name],[Price],[TAX1],[Discount],[Description],[IN_DATE]

           ,[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('Item002','Coffee',40,0,2,'Coffe Might be Hot or Cold user choice',GETDATE(),'SHANU'

           ,GETDATE(),'SHANU')



INSERT INTO [ItemMasters]   ([Item_Code],[Item_Name],[Price],[TAX1],[Discount],[Description],[IN_DATE]

           ,[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('Item003','Chiken Burger',125,2,5,'Spicy',GETDATE(),'SHANU'

           ,GETDATE(),'SHANU')



INSERT INTO [ItemMasters]   ([Item_Code],[Item_Name],[Price],[TAX1],[Discount],[Description],[IN_DATE]

           ,[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('Item004','Potato Fry',15,0,0,'No Comments',GETDATE(),'SHANU'

           ,GETDATE(),'SHANU')

创建Order Master表：

CREATE TABLE [dbo].[OrderMasters](

    [Order_No] [varchar](20) NOT NULL,

    [Table_ID] [varchar](20) NOT NULL,

    [Description] [varchar](200) NOT NULL,

    [IN_DATE] [datetime] NOT NULL,

    [IN_USR_ID] [varchar](20) NOT NULL,

    [UP_DATE] [datetime] NOT NULL,

    [UP_USR_ID] [varchar](20) NOT NULL,

 CONSTRAINT [PK_OrderMasters] PRIMARY KEY CLUSTERED 

(

    [Order_No] ASC

)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]

) ON [PRIMARY]

向Order Master表插入数据：

INSERT INTO [OrderMasters]

           ([Order_No],[Table_ID] ,[Description],[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('Ord_001','T1','',GETDATE(),'SHANU' ,GETDATE(),'SHANU')



INSERT INTO [OrderMasters]

           ([Order_No],[Table_ID] ,[Description],[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('Ord_002','T2','',GETDATE(),'Mak' ,GETDATE(),'MAK')



INSERT INTO [OrderMasters]

           ([Order_No],[Table_ID] ,[Description],[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('Ord_003','T3','',GETDATE(),'RAJ' ,GETDATE(),'RAJ')

创建Order Detail表：

CREATE TABLE [dbo].[OrderDetails](

    [Order_Detail_No] [varchar](20) NOT NULL,

    [Order_No] [varchar](20) CONSTRAINT  fk_OrderMasters FOREIGN KEY REFERENCES OrderMasters(Order_No),

    [Item_Code] [varchar](20) CONSTRAINT  fk_ItemMasters FOREIGN KEY REFERENCES ItemMasters(Item_Code),

    [Notes] [varchar](200) NOT NULL,

    [QTY]  INT NOT NULL,

    [IN_DATE] [datetime] NOT NULL,

    [IN_USR_ID] [varchar](20) NOT NULL,

    [UP_DATE] [datetime] NOT NULL,

    [UP_USR_ID] [varchar](20) NOT NULL,

 CONSTRAINT [PK_OrderDetails] PRIMARY KEY CLUSTERED 

(

    [Order_Detail_No] ASC

)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]

) ON [PRIMARY]



--Now let’s insert the 3 items for the above Order No 'Ord_001'.

INSERT INTO [OrderDetails]

           ([Order_Detail_No],[Order_No],[Item_Code],[Notes],[QTY]

           ,[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('OR_Dt_001','Ord_001','Item001','Need very Cold',3

           ,GETDATE(),'SHANU' ,GETDATE(),'SHANU')



INSERT INTO [OrderDetails]

           ([Order_Detail_No],[Order_No],[Item_Code],[Notes],[QTY]

           ,[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('OR_Dt_002','Ord_001','Item004','very Hot ',2

           ,GETDATE(),'SHANU' ,GETDATE(),'SHANU')



INSERT INTO [OrderDetails]

           ([Order_Detail_No],[Order_No],[Item_Code],[Notes],[QTY]

           ,[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('OR_Dt_003','Ord_001','Item003','Very Spicy',4

           ,GETDATE(),'SHANU' ,GETDATE(),'SHANU')

向Order Detail表插入数据：

INSERT INTO [OrderDetails]

           ([Order_Detail_No],[Order_No],[Item_Code],[Notes],[QTY]

           ,[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('OR_Dt_004','Ord_002','Item002','Need very Hot',2

           ,GETDATE(),'SHANU' ,GETDATE(),'SHANU')



INSERT INTO [OrderDetails]

           ([Order_Detail_No],[Order_No],[Item_Code],[Notes],[QTY]

           ,[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('OR_Dt_005','Ord_002','Item003','very Hot ',2

           ,GETDATE(),'SHANU' ,GETDATE(),'SHANU')



INSERT INTO [OrderDetails]

           ([Order_Detail_No],[Order_No],[Item_Code],[Notes],[QTY]

           ,[IN_DATE],[IN_USR_ID],[UP_DATE],[UP_USR_ID])

     VALUES

           ('OR_Dt_006','Ord_003','Item003','Very Spicy',4

           ,GETDATE(),'SHANU' ,GETDATE(),'SHANU')

2、简单的Select查询语句

Select查询语句是SQL中最基本也是最重要的DML语句之一。那么什么是DML？DML全称Data Manipulation Language（数据操纵语言命令），它可以使用户能够查询数据库以及操作已有数据库中的数据。

下面我们在SQL Server中用select语句来查询我的姓名(Name)：

SELECT 'My Name Is SYED SHANU'

-- With Column Name using 'AS'

SELECT 'My Name Is SYED SHANU' as 'MY NAME'

-- With more then the one Column 

SELECT 'My Name' as 'Column1', 'Is' as 'Column2', 'SYED SHANU' as 'Column3'

在数据表中使用select查询：

-- To Display all the columns from the table we use * operator in select Statement.

Select * from ItemMasters

-- If we need to select only few fields from a table we can use the Column Name in Select Statement.

Select    Item_Code

        ,Item_name as Item

        ,Price

        ,Description

        ,In_DATE

        FROM

        ItemMasters

3、合计和标量函数

合计函数和标量函数都是SQL Server的内置函数，我们可以在select查询语句中使用它们，比如Count(), Max(), Sum(), Upper(), lower(), Round()等等。下面我们用SQL代码来解释这些函数的用法：

select * from ItemMasters

-- Aggregate

-- COUNT() -> returns the Total no of records from table , AVG() returns the Average Value from Colum,MAX() Returns MaX Value from Column

-- ,MIN() returns Min Value from Column,SUM()  sum of total from Column

Select Count(*)  TotalRows,AVG(Price) AVGPrice

        ,MAX(Price) MAXPrice,MIN(Price) MinPrice,Sum(price) PriceTotal 

        FROM ItemMasters



-- Scalar 

-- UCASE() -> Convert to  Upper Case  ,LCASE() -> Convert to Lower Case,

-- SUBSTRING() ->Display selected char from column ->SUBSTRING(ColumnName,StartIndex,LenthofChartoDisplay)

--,LEN() -> lenth of column date,

-- ROUND()  -> Which will round the value

SELECT  UPPER(Item_NAME) Uppers,LOWER(Item_NAME) Lowers,

        SUBSTRING(Item_NAME,2,3) MidValue,LEN(Item_NAME) Lenths 

       ,SUBSTRING(Item_NAME,2,LEN(Item_NAME)) MidValuewithLenFunction, 

        ROUND(Price,0) as Rounded

        FROM ItemMasters

4、日期函数

在我们的项目数据表中基本都会使用到日期列，因此日期函数在项目中扮演着非常重要的角色。有时候我们对日期函数要非常的小心，它随时可以给你带来巨大的麻烦。在项目中，我们要选择合适的日期函数和日期格式，下面是一些SQL日期函数的例子：

-- GETDATE() -> to Display the Current Date and Time

-- Format() -> used to display our date in our requested format

Select GETDATE() CurrentDateTime, FORMAT(GETDATE(),'yyyy-MM-dd') AS DateFormats,

       FORMAT(GETDATE(),'HH-mm-ss')TimeFormats,

       CONVERT(VARCHAR(10),GETDATE(),10) Converts1,

       CONVERT(VARCHAR(24),GETDATE(),113),

       CONVERT(NVARCHAR, getdate(), 106) Converts2 ,-- here we used Convert Function 

      REPLACE(convert(NVARCHAR, getdate(), 106), ' ', '/') Formats-- Here we used replace and --convert functions.

      --first we convert the date to nvarchar and then we replace the '' with '/' 



select * from Itemmasters



Select  ITEM_NAME,IN_DATE CurrentDateTime, FORMAT(IN_DATE,'yyyy-MM-dd') AS DateFormats,

        FORMAT(IN_DATE,'HH-mm-ss')TimeFormats,

        CONVERT(VARCHAR(10),IN_DATE,10) Converts1,

        CONVERT(VARCHAR(24),IN_DATE,113),

        convert(NVARCHAR, IN_DATE, 106) Converts2 ,-- here we used Convert Function 

        REPLACE(convert(NVARCHAR,IN_DATE, 106), ' ', '/') Formats

        FROM Itemmasters

DatePart –>  该函数可以获取年、月、日的信息。

DateADD –>  该函数可以对当前的日期进行加减。

DateDiff  –>  该函数可以比较2个日期。

--Datepart DATEPART(dateparttype,yourDate)

SELECT DATEPART(yyyy,getdate()) AS YEARs ,

DATEPART(mm,getdate()) AS MONTHS,

DATEPART(dd,getdate()) AS Days,

DATEPART(week,getdate()) AS weeks,

DATEPART(hour,getdate()) AS hours



--Days Add to add or subdtract date from a selected date.

SELECT GetDate()CurrentDate,DATEADD(day,12,getdate()) AS AddDays ,

 DATEADD(day,-4,getdate()) AS FourDaysBeforeDate 



 -- DATEDIFF() -> to display the Days between 2 dates

 select DATEDIFF(year,'2003-08-05',getdate())  yearDifferance , 

  DATEDIFF(day,DATEADD(day,-24,getdate()),getdate()) daysDifferent,

 DATEDIFF(month,getdate(),DATEADD(Month,6,getdate())) MonthDifferance

5、其他Select函数

Top —— 结合select语句，Top函数可以查询头几条和末几条的数据记录。

Order By —— 结合select语句，Order By可以让查询结果按某个字段正序和逆序输出数据记录。

--Top to Select Top first and last records using Select Statement.

Select * FROM ItemMasters

--> First Display top 2 Records

Select TOP 2 Item_Code

             ,Item_name as Item

             ,Price

             ,Description

             ,In_DATE

FROM ItemMasters

--> to Display the Last to Records we need to use the Order By Clause

-- order By to display Records in assending or desending order by the columns

Select TOP 2  Item_Code

             ,Item_name as Item

             ,Price

             ,Description

             ,In_DATE

FROM ItemMasters

ORDER BY Item_Code DESC

Distinct —— distinct关键字可以过滤重复的数据记录。

Select * FROM ItemMasters

--Distinct -> To avoid the Duplicate records we use the distinct in select statement

-- for example in this table we can see here we have the duplicate record 'Chiken Burger'

-- but with different Item_Code when i use the below select statement see what happen



Select   Item_name as Item

        ,Price

        ,Description    

        ,IN_USR_ID    

        FROM ItemMasters

-- here we can see the Row No 3 and 5 have the duplicate record to avoid this we use the distinct Keyword in select statement.



select Distinct Item_name as Item

                ,Price

                ,Description    

                ,IN_USR_ID    

                 FROM ItemMasters

Where子句在SQL Select查询语句中非常重要，为什么要使用where子句？什么时候使用where子句？where子句是利用一些条件来过滤数据结果集。

下面我们从10000条数据记录中查询Order_No为某个值或者某个区间的数据记录，另外还有其他的条件。

Select * from ItemMasters

Select * from OrderDetails

--Where -> To display the data with certain conditions

-- Now below example which will display all the records which has Item_Name='Coke'

select * FROM ItemMasters WHERE ITEM_NAME='COKE'

-- If we want display all the records Iten_Name which Starts with 'C' then we use Like in where clause.

SELECT * FROM ItemMasters WHERE ITEM_NAME Like 'C%'



--> here we display the ItemMasters where the price will be greater then or equal to 40.

--> to use more then one condition we can Use And or Or operator.

--If we want to check the data between to date range then we can use Between Operator in Where Clause.

select Item_name as Item

        ,Price

        ,Description    

        ,IN_USR_ID    

         FROM ItemMasters

         WHERE

            ITEM_NAME Like 'C%' 

            AND 

            price >=40

--> here we display the OrderDetails where the Qty will be greater 3



Select * FROM OrderDetails WHERE qty>3

Where – In 子句

-- In clause -> used to display the data which is in the condition

select *

        FROM ItemMasters

        WHERE

        Item_name IN ('Coffee','Chiken Burger')



-- In clause with Order By - Here we display the in descending order.

select *

        FROM ItemMasters

        WHERE

        Item_name IN ('Coffee','Chiken Burger')

        ORDER BY Item_Code Desc

Where – Between子句

-- between  -> Now if we want to display the data between to date range then we use betweeen keyword

select * FROM ItemMasters



select * FROM ItemMasters

         WHERE

         In_Date BETWEEN '2014-09-22 15:59:02.853' AND '2014-09-22 15:59:02.853'



select * FROM ItemMasters

         WHERE

         ITEM_NAME Like 'C%' 

         AND

         In_Date BETWEEN '2014-09-22 15:59:02.853' AND '2014-09-22 15:59:02.853'

查询某个条件区间的数据，我们常常使用between子句。

7、Group By 子句

Group By子句可以对查询的结果集按指定字段分组：

--Group By -> To display the data with group result.Here we can see we display all the AQggregate result by Item Name

Select ITEM_NAME,Count(*)  TotalRows,AVG(Price) AVGPrice

        ,MAX(Price) MAXPrice,MIN(Price) MinPrice,Sum(price) PriceTotal 

        FROM

        ItemMasters

        GROUP BY ITEM_NAME



-- Here this group by will combine all the same Order_No result and make the total or each order_NO

Select Order_NO,Sum(QTy) as TotalQTY 

    FROM OrderDetails

    where qty>=2

    GROUP BY Order_NO



-- Here the Total will be created by order_No and Item_Code

Select Order_NO,Item_Code,Sum(QTy) as TotalQTY 

    FROM OrderDetails

    where qty>=2

    GROUP BY Order_NO,Item_Code

    Order By Order_NO Desc,Item_Code

Group By & Having 子句

--Group By Clause -- here this will display all the Order_no 

Select Order_NO,Sum(QTy) as TotalQTY 

    FROM OrderDetails

    GROUP BY Order_NO



-- Having Clause-- This will avoid the the sum(qty) less then 4    

Select Order_NO,Sum(QTy) as TotalQTY 

    FROM OrderDetails

    GROUP BY Order_NO

    HAVING Sum(QTy) >4

8、子查询

子查询一般出现在where内连接查询和嵌套查询中，select、update和delete语句中均可以使用。

--Sub Query -- Here we used the Sub query in where clause to get all the Item_Code where the price>40 now this sub 

--query reslut we used in our main query to filter all the records which Item_code from Subquery result

SELECT * FROM ItemMasters 

         WHERE Item_Code IN 

        (SELECT Item_Code FROM ItemMasters WHERE price > 40) 



-- Sub Query with Insert Statement

INSERT INTO ItemMasters           ([Item_Code] ,[Item_Name],[Price],[TAX1],[Discount],[Description],[IN_DATE]

           ,[IN_USR_ID],[UP_DATE] ,[UP_USR_ID])

    Select 'Item006'

           ,Item_Name,Price+4,TAX1,Discount,Description

           ,GetDate(),'SHANU',GetDate(),'SHANU'

           from ItemMasters

           where Item_code='Item002'       



--After insert we can see the result as 

        Select * from ItemMasters

9、连接查询

到目前为止我们接触了不少单表的查询语句，现在我们来使用连接查询获取多个表的数据。

简单的join语句：

--Now we have used the simple join with out any condition this will display all the

-- records with duplicate data to avaoid this we see our next example with condition

SELECT * FROM Ordermasters,OrderDetails

-- Simple Join with Condition  now here we can see the duplicate records now has been avoided by using the where checing with both table primaryKey field

SELECT * 

        FROM

        Ordermasters as M, OrderDetails as D

        where M.Order_NO=D.Order_NO

        and M.Order_NO='Ord_001'



-- Now to make more better understanding we need to select the need fields from both 

--table insted of displaying all column.

SELECT M.order_NO,M.Table_ID,D.Order_detail_no,Item_code,Notes,Qty

                FROM 

                Ordermasters as M, OrderDetails as D 

                where M.Order_NO=D.Order_NO                  

 -- Now lets Join 3 table

 SELECT     M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,

                I.Price*D.Qty as TotalPrice

                FROM 

                Ordermasters as M, OrderDetails as D,ItemMasters as I 

                where 

                M.Order_NO=D.Order_NO AND D.Item_Code=I.Item_Code

Inner Join,Left Outer Join,Right Outer Join and Full outer Join

下面是各种类型的连接查询代码：

--INNER JOIN 

--This will display the records which in both table Satisfy here i have used Like in where class which display the 

SELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPrice

        FROM 

        Ordermasters as M Inner JOIN OrderDetails as D 

        ON M.Order_NO=D.Order_NO

        INNER JOIN     ItemMasters as I 

        ON   D.Item_Code=I.Item_Code

        WHERE

        M.Table_ID like 'T%'

--LEFT OUTER JOIN 

--This will display the records which Left side table Satisfy

 SELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPrice

        FROM 

        Ordermasters as M LEFT OUTER JOIN OrderDetails as D 

        ON M.Order_NO=D.Order_NO

        LEFT OUTER JOIN     ItemMasters as I 

        ON   D.Item_Code=I.Item_Code

        WHERE

        M.Table_ID like 'T%'

--RIGHT OUTER JOIN 

--This will display the records which Left side table Satisfy

 SELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPrice

        FROM 

        Ordermasters as M RIGHT OUTER JOIN OrderDetails as D 

        ON M.Order_NO=D.Order_NO

        RIGHT OUTER JOIN     ItemMasters as I 

        ON   D.Item_Code=I.Item_Code

        WHERE

        M.Table_ID like 'T%'



--FULL OUTER JOIN 

--This will display the records which Left side table Satisfy

 SELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPrice

        FROM 

        Ordermasters as M FULL OUTER JOIN OrderDetails as D 

        ON M.Order_NO=D.Order_NO

        FULL OUTER JOIN     ItemMasters as I 

        ON   D.Item_Code=I.Item_Code

        WHERE

        M.Table_ID like 'T%'

 

10、Union合并查询

Union查询可以把多张表的数据合并起来，Union只会把唯一的数据查询出来，而Union ALL则会把重复的数据也查询出来。

Select column1,Colum2 from Table1

Union

Select Column1,Column2 from Table2



Select column1,Colum2 from Table1

Union All

Select Column1,Column2 from Table2

具体的例子如下：

--Select with different where condition which display the result as 2 Table result

select Item_Code,Item_Name,Price,Description FROM ItemMasters where price <=44

select Item_Code,Item_Name,Price,Description FROM ItemMasters where price >44



-- Union with same table but with different where condition now which result as one table which combine both the result.

select Item_Code,Item_Name,Price,Description FROM ItemMasters where price <=44

UNION

select Item_Code,Item_Name,Price,Description FROM ItemMasters where price >44



-- Union ALL with Join sample

 SELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPrice

    FROM 

        Ordermasters as M (NOLOCK)   Inner JOIN OrderDetails as D  

        ON M.Order_NO=D.Order_NO INNER JOIN     ItemMasters as I 

        ON   D.Item_Code=I.Item_Code WHERE        I.Price <=44        

Union ALL

 SELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPrice

    FROM 

        Ordermasters as M (NOLOCK)   Inner JOIN OrderDetails as D

        ON M.Order_NO=D.Order_NO    INNER JOIN     ItemMasters as I

        ON   D.Item_Code=I.Item_Code    WHERE    I.Price>44

11、公用表表达式（CTE）——With语句

CTE可以看作是一个临时的结果集，可以在接下来的一个SELECT,INSERT,UPDATE,DELETE,MERGE语句中被多次引用。使用公用表达式可以让语句更加清晰简练。

declare @sDate datetime,

        @eDate datetime;



select  @sDate = getdate()-5,

        @eDate = getdate()+16;

--select @sDate StartDate,@eDate EndDate

;with cte as

   (

      select @sDate StartDate,'W'+convert(varchar(2),

            DATEPART( wk, @sDate))+'('+convert(varchar(2),@sDate,106)+')' as 'SDT'     

  union all

       select  dateadd(DAY, 1, StartDate) ,

              'W'+convert(varchar(2),DATEPART( wk, StartDate))+'('+convert(varchar(2),

               dateadd(DAY, 1, StartDate),106)+')' as 'SDT'   

  FROM  cte

  WHERE dateadd(DAY, 1, StartDate)<=  @eDate 

    )

select * from cte

option (maxrecursion 0)

12、视图

很多人对视图View感到很沮丧，因为它看起来跟select语句没什么区别。在视图中我们同样可以使用select查询语句，但是视图对我们来说依然非常重要。

假设我们要联合查询4张表中的20几个字段，那么这个select查询语句会非常复杂。但是这样的语句我们在很多地方都需要用到，如果将它编写成视图，那么使用起来会方便很多。利用视图查询有以下几个优点：

• 一定程度上提高查询速度
• 可以对一些字段根据不同的权限进行屏蔽，因此提高了安全性
• 对多表的连接查询会非常方便

下面是一个视图的代码例子：

CREATE 

VIEW viewname

AS

Select ColumNames from yourTable



Example : 

-- Here we create view for our Union ALL example

Create 

VIEW myUnionVIEW

AS

 SELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,

        I.Price*D.Qty as TotalPrice

        FROM 

          Ordermasters as M  Inner JOIN OrderDetails as D 

          ON M.Order_NO=D.Order_NO INNER JOIN ItemMasters as I 

          ON   D.Item_Code=I.Item_Code WHERE    I.Price <=44        

Union ALL

 SELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,

        I.Price*D.Qty as TotalPrice

        FROM 

          Ordermasters as M  Inner JOIN OrderDetails as D 

          ON M.Order_NO=D.Order_NO INNER JOIN ItemMasters as I 

          ON   D.Item_Code=I.Item_Code    WHERE    I.Price>44



-- View Select query

Select * from myUnionVIEW

-- We can also use the View to display with where condition and with selected fields 

Select order_Detail_NO,Table_ID,Item_Name,Price from myUnionVIEW where price >40

13、Pivot行转列

Pivot可以帮助你实现数据行转换成数据列，具体用法如下：

-- Simple Pivot Example 

SELECT *  FROM ItemMasters 

PIVOT(SUM(Price)       

 FOR ITEM_NAME IN ([Chiken Burger], Coffee,Coke)) AS PVTTable



-- Pivot with detail example

SELECT *

FROM (

    SELECT 

       ITEM_NAME, 

        price as TotAmount 

    FROM ItemMasters



) as s

PIVOT

(

    SUM(TotAmount)

    FOR [ITEM_NAME] IN ([Chiken Burger], [Coffee],[Coke])

)AS MyPivot

14、存储过程

我经常看到有人提问如何在SQL Server中编写多条查询的SQL语句，然后将它们使用到C#程序中去。存储过程就可以完成这样的功能，存储过程可以将多个SQL查询聚集在一起，创建存储过程的基本结构是这样的：

CREATE PROCEDURE [ProcedureName]                                              



AS                                                                

BEGIN

-- Select or Update or Insert query.

END



To execute SP we use

exec ProcedureName

创建一个没有参数的存储过程：

-- =============================================                                                                

-- Author      : Shanu                                                                

-- Create date : 2014-09-15                                                                

-- Description : To Display Pivot Data                                                        

-- Latest                                                                

-- Modifier    : Shanu                                                                

-- Modify date : 2014-09-15                                                                 

-- =============================================                                                                

-- exec USP_SelectPivot                                 

-- =============================================                                                           

Create PROCEDURE [dbo].[USP_SelectPivot]      

AS                                                                

BEGIN                                                 

   DECLARE @MyColumns AS NVARCHAR(MAX),

    @SQLquery  AS NVARCHAR(MAX)

-- here first we get all the ItemName which should be display in Columns we use this in our necxt pivot query

select @MyColumns = STUFF((SELECT ',' + QUOTENAME(Item_NAME) 

                    FROM ItemMasters

                    GROUP BY Item_NAME

                    ORDER BY Item_NAME

            FOR XML PATH(''), TYPE

            ).value('.', 'NVARCHAR(MAX)') 

        ,1,1,'')

-- here we use the above all Item name to disoplay its price as column and row display

set @SQLquery = N'SELECT ' + @MyColumns + N' from 

             (

                 SELECT 

       ITEM_NAME, 

        price as TotAmount 

    FROM ItemMasters

            ) x

            pivot 

            (

                 SUM(TotAmount)

                for ITEM_NAME in (' + @MyColumns + N')

            ) p '



exec sp_executesql @SQLquery;           



   RETURN                                              

    END

15、函数Function

之前我们介绍了MAX(),SUM(), GetDate()等最基本的SQL函数，现在我们来看看如何创建自定义SQL函数。创建函数的格式如下：

Create Function functionName

As

Begin

END

下面是一个简单的函数示例：

-- =============================================                                                                

-- Author      : Shanu                                                                

-- Create date : 2014-09-15                                                                

-- Description : To Display Pivot Data                                                        

-- Latest                                                                

-- Modifier    : Shanu                                                                

-- Modify date : 2014-09-15                                                                 



Alter FUNCTION [dbo].[ufnSelectitemMaster]()

RETURNS int 

AS 

-- Returns total Row count of Item Master.



BEGIN

  DECLARE @RowsCount AS int;



Select @RowsCount= count(*)+1 from ItemMasters

 RETURN @RowsCount;



END



-- to View Function we use select and fucntion Name

select [dbo].[ufnSelectitemMaster]()

下面的一个函数可以实现从给定的日期中得到当前月的最后一天：

-- =============================================                                                                

-- Author      : Shanu                                                                

-- Create date : 2014-09-15                                                                

-- Description : To Display Pivot Data                                                        

-- Latest                                                                

-- Modifier    : Shanu                                                                

-- Modify date : 2014-09-15    



ALTER FUNCTION [dbo].[ufn_LastDayOfMonth]

(

   @DATE NVARCHAR(10) 

)

RETURNS NVARCHAR(10)

AS

BEGIN

   RETURN CONVERT(NVARCHAR(10), DATEADD(D, -1, DATEADD(M, 1, CAST(SUBSTRING(@DATE,1,7) + '-01' AS DATETIME))), 120)

END

SELECT dbo.ufn_LastDayOfMonth('2014-09-01')AS LastDay