1、創(chuàng)建表和數(shù)據(jù)插入SQL

我們在開始創(chuàng)建數(shù)據(jù)表和向表中插入演示數(shù)據(jù)之前，我想給大家解釋一下實(shí)時數(shù)據(jù)表的設(shè)計(jì)理念，這樣也許能幫助大家能更好的理解SQL查詢。

在數(shù)據(jù)庫設(shè)計(jì)中，有一條非常重要的規(guī)則就是要正確建立主鍵和外鍵的關(guān)系。

現(xiàn)在我們來創(chuàng)建幾個餐廳訂單管理的數(shù)據(jù)表，一共用到3張數(shù)據(jù)表，Item Master表、Order Master表和Order Detail表。

創(chuàng)建表：

創(chuàng)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表插入數(shù)據(jù)：

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')

創(chuàng)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表插入數(shù)據(jù)：

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')

創(chuàng)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表插入數(shù)據(jù)：

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、簡單的Select查詢語句

Select查詢語句是SQL中最基本也是最重要的DML語句之一。那么什么是DML？DML全稱Data Manipulation Language（數(shù)據(jù)操縱語言命令），它可以使用戶能夠查詢數(shù)據(jù)庫以及操作已有數(shù)據(jù)庫中的數(shù)據(jù)。

下面我們在SQL Server中用select語句來查詢我的姓名(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'

在數(shù)據(jù)表中使用select查詢：

-- 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_DATEFROMItemMasters

3、合計(jì)和標(biāo)量函數(shù)

合計(jì)函數(shù)和標(biāo)量函數(shù)都是SQL Server的內(nèi)置函數(shù)，我們可以在select查詢語句中使用它們，比如Count(), Max(), Sum(), Upper(), lower(), Round()等等。下面我們用SQL代碼來解釋這些函數(shù)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 RoundedFROM ItemMasters

4、日期函數(shù)

在我們的項(xiàng)目數(shù)據(jù)表中基本都會使用到日期列，因此日期函數(shù)在項(xiàng)目中扮演著非常重要的角色。有時候我們對日期函數(shù)要非常的小心，它隨時可以給你帶來巨大的麻煩。在項(xiàng)目中，我們要選擇合適的日期函數(shù)和日期格式，下面是一些SQL日期函數(shù)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 ItemmastersSelect 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), ' ', '/') FormatsFROM Itemmasters

DatePart –> ?該函數(shù)可以獲取年、月、日的信息。

DateADD –> ?該函數(shù)可以對當(dāng)前的日期進(jìn)行加減。

DateDiff ?–> ?該函數(shù)可以比較2個日期。

--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 datesselect 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函數(shù)

Top —— 結(jié)合select語句，Top函數(shù)可以查詢頭幾條和末幾條的數(shù)據(jù)記錄。

Order By —— 結(jié)合select語句，Order By可以讓查詢結(jié)果按某個字段正序和逆序輸出數(shù)據(jù)記錄。

--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關(guān)鍵字可以過濾重復(fù)的數(shù)據(jù)記錄。

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 happenSelect 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子句

Where子句在SQL Select查詢語句中非常重要，為什么要使用where子句？什么時候使用where子句？where子句是利用一些條件來過濾數(shù)據(jù)結(jié)果集。

下面我們從10000條數(shù)據(jù)記錄中查詢Order_No為某個值或者某個區(qū)間的數(shù)據(jù)記錄，另外還有其他的條件。

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 ItemMastersWHEREITEM_NAME Like 'C%' AND price >=40 --> here we display the OrderDetails where the Qty will be greater 3Select * FROM OrderDetails WHERE qty>3

Where – In 子句

-- In clause -> used to display the data which is in the condition select *FROM ItemMastersWHEREItem_name IN ('Coffee','Chiken Burger')-- In clause with Order By - Here we display the in descending order. select *FROM ItemMastersWHEREItem_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 ItemMastersselect * FROM ItemMastersWHEREIn_Date BETWEEN '2014-09-22 15:59:02.853' AND '2014-09-22 15:59:02.853'select * FROM ItemMastersWHEREITEM_NAME Like 'C%' ANDIn_Date BETWEEN '2014-09-22 15:59:02.853' AND '2014-09-22 15:59:02.853'

查詢某個條件區(qū)間的數(shù)據(jù)，我們常常使用between子句。

7、Group By 子句

Group By子句可以對查詢的結(jié)果集按指定字段分組：

--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 FROMItemMastersGROUP 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 OrderDetailswhere qty>=2GROUP 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 OrderDetailswhere qty>=2GROUP BY Order_NO,Item_CodeOrder 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 OrderDetailsGROUP BY Order_NO-- Having Clause-- This will avoid the the sum(qty) less then 4 Select Order_NO,Sum(QTy) as TotalQTY FROM OrderDetailsGROUP BY Order_NOHAVING Sum(QTy) >4

8、子查詢

子查詢一般出現(xiàn)在where內(nèi)連接查詢和嵌套查詢中，select、update和delete語句中均可以使用。

--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 ItemMasterswhere Item_code='Item002' --After insert we can see the result as Select * from ItemMasters

9、連接查詢

到目前為止我們接觸了不少單表的查詢語句，現(xiàn)在我們來使用連接查詢獲取多個表的數(shù)據(jù)。

簡單的join語句：

--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 * FROMOrdermasters as M, OrderDetails as Dwhere M.Order_NO=D.Order_NOand 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,QtyFROM Ordermasters as M, OrderDetails as D where M.Order_NO=D.Order_NO -- Now lets Join 3 tableSELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPriceFROM 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

下面是各種類型的連接查詢代碼：

--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 TotalPriceFROM Ordermasters as M Inner JOIN OrderDetails as D ON M.Order_NO=D.Order_NOINNER JOIN ItemMasters as I ON D.Item_Code=I.Item_CodeWHEREM.Table_ID like 'T%' --LEFT OUTER JOIN --This will display the records which Left side table SatisfySELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPriceFROM Ordermasters as M LEFT OUTER JOIN OrderDetails as D ON M.Order_NO=D.Order_NOLEFT OUTER JOIN ItemMasters as I ON D.Item_Code=I.Item_CodeWHEREM.Table_ID like 'T%' --RIGHT OUTER JOIN --This will display the records which Left side table SatisfySELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPriceFROM Ordermasters as M RIGHT OUTER JOIN OrderDetails as D ON M.Order_NO=D.Order_NORIGHT OUTER JOIN ItemMasters as I ON D.Item_Code=I.Item_CodeWHEREM.Table_ID like 'T%'--FULL OUTER JOIN --This will display the records which Left side table SatisfySELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPriceFROM Ordermasters as M FULL OUTER JOIN OrderDetails as D ON M.Order_NO=D.Order_NOFULL OUTER JOIN ItemMasters as I ON D.Item_Code=I.Item_CodeWHEREM.Table_ID like 'T%'

10、Union合并查詢

Union查詢可以把多張表的數(shù)據(jù)合并起來，Union只會把唯一的數(shù)據(jù)查詢出來，而Union ALL則會把重復(fù)的數(shù)據(jù)也查詢出來。

Select column1,Colum2 from Table1 Union Select Column1,Column2 from Table2Select column1,Colum2 from Table1 Union All Select Column1,Column2 from Table2

具體的例子如下：

--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 sampleSELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPriceFROM 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 ALLSELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPriceFROM Ordermasters as M (NOLOCK) Inner JOIN OrderDetails as DON M.Order_NO=D.Order_NO INNER JOIN ItemMasters as ION D.Item_Code=I.Item_Code WHERE I.Price>44

11、公用表表達(dá)式（CTE）——With語句

CTE可以看作是一個臨時的結(jié)果集，可以在接下來的一個SELECT,INSERT,UPDATE,DELETE,MERGE語句中被多次引用。使用公用表達(dá)式可以讓語句更加清晰簡練。

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 allselect dateadd(DAY, 1, StartDate) ,'W'+convert(varchar(2),DATEPART( wk, StartDate))+'('+convert(varchar(2),dateadd(DAY, 1, StartDate),106)+')' as 'SDT' FROM cteWHERE dateadd(DAY, 1, StartDate)<= @eDate ) select * from cte option (maxrecursion 0)

12、視圖

很多人對視圖View感到很沮喪，因?yàn)樗雌饋砀鷖elect語句沒什么區(qū)別。在視圖中我們同樣可以使用select查詢語句，但是視圖對我們來說依然非常重要。

假設(shè)我們要聯(lián)合查詢4張表中的20幾個字段，那么這個select查詢語句會非常復(fù)雜。但是這樣的語句我們在很多地方都需要用到，如果將它編寫成視圖，那么使用起來會方便很多。利用視圖查詢有以下幾個優(yōu)點(diǎn)：

• 一定程度上提高查詢速度
• 可以對一些字段根據(jù)不同的權(quán)限進(jìn)行屏蔽，因此提高了安全性
• 對多表的連接查詢會非常方便

下面是一個視圖的代碼例子：

CREATE VIEW viewname AS Select ColumNames from yourTableExample : -- Here we create view for our Union ALL example Create VIEW myUnionVIEW ASSELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPriceFROM 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 ALLSELECT M.order_NO,M.Table_ID,D.Order_detail_no,I.Item_Name,D.Notes,D.Qty,I.Price,I.Price*D.Qty as TotalPriceFROM 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行轉(zhuǎn)列

Pivot可以幫助你實(shí)現(xiàn)數(shù)據(jù)行轉(zhuǎn)換成數(shù)據(jù)列，具體用法如下：

-- 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、存儲過程

我經(jīng)常看到有人提問如何在SQL Server中編寫多條查詢的SQL語句，然后將它們使用到C#程序中去。存儲過程就可以完成這樣的功能，存儲過程可以將多個SQL查詢聚集在一起，創(chuàng)建存儲過程的基本結(jié)構(gòu)是這樣的：

CREATE PROCEDURE [ProcedureName] AS BEGIN -- Select or Update or Insert query. ENDTo execute SP we use exec ProcedureName

創(chuàng)建一個沒有參數(shù)的存儲過程：

-- ============================================= -- 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 ItemMastersGROUP BY Item_NAMEORDER BY Item_NAMEFOR 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) xpivot (SUM(TotAmount)for ITEM_NAME in (' + @MyColumns + N')) p 'exec sp_executesql @SQLquery; RETURN END

15、函數(shù)Function

之前我們介紹了MAX(),SUM(), GetDate()等最基本的SQL函數(shù)，現(xiàn)在我們來看看如何創(chuàng)建自定義SQL函數(shù)。創(chuàng)建函數(shù)的格式如下：

Create Function functionName As Begin END

下面是一個簡單的函數(shù)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.BEGINDECLARE @RowsCount AS int;Select @RowsCount= count(*)+1 from ItemMastersRETURN @RowsCount;END-- to View Function we use select and fucntion Name select [dbo].[ufnSelectitemMaster]()

下面的一個函數(shù)可以實(shí)現(xiàn)從給定的日期中得到當(dāng)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 BEGINRETURN 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

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