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http://www.codeweblog.com/15个初学者必看的基础sql查询语句/

林伟琨
 林伟琨
发布于 2016/06/14 11:54
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本文将分享15个初学者必看的基础SQL查询语句,都很基础,但是你不一定都会,所以好好看看吧。 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 NOT NULL, [Item_Name] varchar NOT NULL, [Price] Int NOT NULL, [TAX1] Int NOT NULL, [Discount] Int NOT NULL, [Description] varchar NOT NULL, [IN_DATE] [datetime] NOT NULL, [IN_USR_ID] varchar NOT NULL, [UP_DATE] [datetime] NOT NULL, [UP_USR_ID] varchar 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 NOT NULL, [Table_ID] varchar NOT NULL, [Description] varchar NOT NULL, [IN_DATE] [datetime] NOT NULL, [IN_USR_ID] varchar NOT NULL, [UP_DATE] [datetime] NOT NULL, [UP_USR_ID] varchar 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 NOT NULL, [Order_No] varchar CONSTRAINT fk_OrderMasters FOREIGN KEY REFERENCES OrderMasters(Order_No), [Item_Code] varchar CONSTRAINT fk_ItemMasters FOREIGN KEY REFERENCES ItemMasters(Item_Code), [Notes] varchar NOT NULL, [QTY] INT NOT NULL, [IN_DATE] [datetime] NOT NULL, [IN_USR_ID] varchar NOT NULL, [UP_DATE] [datetime] NOT NULL, [UP_USR_ID] varchar 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 6、Where子句 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 15个初学者必看的基础SQL查询语句 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.PriceD.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.PriceD.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.PriceD.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.PriceD.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.PriceD.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.PriceD.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.PriceD.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.PriceD.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

本文转载自:http://www.codeweblog.com/15个初学者必看的基础sql查询语句/

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