15 basic SQL query statements that beginners must read

　1. Create a table and insert data into SQL

　Before we start to create a data table and insert demo data into the table, I would like to explain to you the design concept of the real-time data table, which may help you better understand SQL. Inquire.

　In database design, a very important rule is to correctly establish the relationship between primary keys and foreign keys.

Now let’s create several data tables for restaurant order management. A total of 3 data tables are used, the Item Master table, the Order Master table and the Order Detail table.

Create table:

Create Item Master table:

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]

Insert data into Item Master table:

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')

Create Order Master table:

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]

Insert data into Order Master table:

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')

Create Order Detail table:

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')

　Insert data into the Order Detail table:

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. Simple Select query statement

　The Select query statement is one of the most basic and important DML statements in SQL. So what is DML? DML stands for Data Manipulation Language (Data Manipulation Language), which enables users to query databases and manipulate data in existing databases.

　 Next we use the select statement in SQL Server to query my name (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'

Use select query in the data table:

-- 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. Total and scalar functions

The total function and scalar function are both SQL Server's built-in functions, we can use them in select query statements, such as Count(), Max(), Sum(), Upper(), lower(), Round(), etc. Below we use SQL code to explain the usage of these functions:

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. Date function

　 Date columns are basically used in our project data tables, so date functions play a very important role in the project. Sometimes we have to be very careful with date functions, they can cause you huge trouble at any time. In the project, we need to choose the appropriate date function and date format. Here are some examples of SQL date functions:

-- 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 –> This function can obtain the year, month, and day information.

　DateADD –> This function can add and subtract the current date.

　DateDiff –> This function can compare 2 dates.

--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. Other Select functions

　 Top - Combined with the select statement, the Top function can query the first few and last few data records.

　Order By - Combined with the select statement, Order By allows the query results to output data records in positive and negative order in a certain field.

-

-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 - The distinct keyword can filter duplicate data records.

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

6. Where clause

The Where clause is very important in the SQL Select query statement. Why use the where clause? When to use where clause? The where clause uses some conditions to filter the data result set.

　 Next we query the data records whose Order_No is a certain value or a certain range from 10,000 data records, and there are other conditions.

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 clause

-- 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 clause

-- 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'

　 To query data in a certain condition range, we often use the between clause.

　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 WHEREI.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_NOINNER JOIN ItemMasters as I
ON   D.Item_Code=I.Item_CodeWHEREI.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 WHEREI.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_CodeWHEREI.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