sql2

/**************************/
/*      SQL DML           */
/*      AUTHER:WL         */
/**************************/

USE Northwind

SELECT * FROM
(
  SELECT TOP 10 PERCENT orderid , customerid
  FROM dbo.Orders
  ORDER BY orderid
)
AS D
-- 以上是非合理的SQL，ORDER BY 返回游标不应作为表变量

--SQL2005 FROM 子句的表操作：JOIN , APPLY ,PIVOT 和 UNPIVOT

SELECT * FROM dbo.Customers

SELECT * FROM dbo.Orders

--CROSS APPLY
--返回消费者两个最新的订单
SELECT C.customerid ,city,orderid
FROM dbo.Customers AS C
CROSS APPLY
(
 SELECT TOP(2) orderid ,customerid
 FROM dbo.Orders AS O
 WHERE O.customerid = C.customerid
 ORDER BY orderid DESC
) AS CA

--OUTER APPLY
--返回消费者两个最新的订单，同时返回没有订单的消费者
SELECT C.customerid ,city ,orderid
FROM dbo.Customers AS C
OUTER APPLY
(SELECT TOP(2) orderid ,customerid
 FROM dbo.Orders AS O
 WHERE O.customerid = C.customerid
 ORDER BY orderid DESC ) AS OA

SELECT C.customerid ,city,
CASE
  WHEN COUNT(orderid) = 0 THEN 'no_orders'
  WHEN COUNT(orderid) = 2 THEN 'up_to_two_orders'
  WHEN COUNT(orderid) > 2 THEN 'more_to_two_orders'
END AS category
FROM dbo.Customers AS C LEFT OUTER JOIN dbo.Orders AS O
ON C.customerid = O.customerid
GROUP BY C.customerid ,city

-- use  SQL 2005 PIVORT
SELECT city , no_orders ,up_to_two_orders,more_to_two_orders
FROM
( 
SELECT C.customerid ,city,
CASE
  WHEN COUNT(orderid) = 0 THEN 'no_orders'
  WHEN COUNT(orderid) = 2 THEN 'up_to_two_orders'
  WHEN COUNT(orderid) > 2 THEN 'more_to_two_orders'
END AS category
FROM dbo.Customers AS C LEFT OUTER JOIN dbo.Orders AS O
ON C.customerid = O.customerid
GROUP BY C.customerid ,city
)
AS D  PIVOT(COUNT(customerid) FOR category
IN(
  [no_orders],
  [up_to_two_orders],
  [more_to_two_orders]
)) AS P

SELECT city,
  COUNT(CASE WHEN category = 'no_orders' THEN customerid END) AS [no_orders] ,
  COUNT(CASE WHEN category = 'up_to_two_orders' THEN customerid END) AS [up_to_two_orders],
  COUNT(CASE WHEN category = 'more_to_two_orders' THEN customerid END) AS [more_to_two_orders]
FROM (

SELECT C.customerid ,city,
CASE
  WHEN COUNT(orderid) = 0 THEN 'no_orders'
  WHEN COUNT(orderid) = 2 THEN 'up_to_two_orders'
  WHEN COUNT(orderid) > 2 THEN 'more_to_two_orders'
END AS category
FROM dbo.Customers AS C LEFT OUTER JOIN dbo.Orders AS O
ON C.customerid = O.customerid
GROUP BY C.customerid ,city
) AS D
GROUP BY city

-- use UNPIVOT

-- use OVER

SELECT orderid ,customerid,
COUNT(*) OVER(PARTITION BY customerid ) AS num_orders
FROM dbo.Orders
WHERE customerid IS NOT NULL
AND orderid % 2 = 1

SELECT orderid ,customerid FROM dbo.Orders
WHERE customerid IS NOT NULL
AND orderid % 2 = 1
ORDER BY COUNT(*) OVER(PARTITION BY customerid ) DESC

--UNION
SELECT 'O' AS letter , customerid ,orderid FROM  dbo.Orders
WHERE customerid LIKE '%o%'

UNION ALL

SELECT 'S' AS letter ,customerid ,orderid FROM  dbo.Orders
WHERE customerid LIKE '%s%'

ORDER BY letter ,customerid ,orderid

--EXCEPTF 返回不重复的数据
SELECT customerid FROM  dbo.Customers
EXCEPT
SELECT customerid FROM  dbo.Orders

-- INTERSECT  返回重复的数据
SELECT customerid FROM  dbo.Customers
INTERSECT
SELECT customerid FROM  dbo.Orders
 
USE Northwind

SELECT  C.CustomerID , COUNT(O.OrderID) AS NumOrders
FROM dbo.Customers AS C
LEFT OUTER JOIN dbo.Orders AS O ON C.CustomerID = O.CustomerID
WHERE  C.city = 'london'
GROUP BY C.customerID
HAVING COUNT(O.Orderid) > 5
ORDER BY NumOrders

-- 优化事件
SELECT * FROM sys.dm_exec _query_optimizer_info

USE Northwind
SELECT * INTO #TEMPWL FROM dbo.Orders

SELECT * FROM #TEMPWL

DROP TABLE #TEMPWL

GO

SELECT * FROM dbo.Table_1wl

SELECT * FROM dbo.Table_2wl
-- 复制表到另一张表
SELECT * INTO  #Table_2wl FROM   dbo.Table_1wl

SELECT * FROM  #Table_2wl

--将一张表中的内容批量插入到另一张表
INSERT INTO Table_2wl SELECT T1,T2 FROM  dbo.Table_1wl

SELECT * FROM  dbo.Table_2wl

USE Northwind
SELECT
 [Order Details].OrderID,
 Products.ProductName,
 [Order Details].Quantity,
 [Order Details].UnitPrice
FROM dbo.[Order Details]
LEFT OUTER JOIN dbo.Products
ON [Order Details].ProductID = Products.ProductID
WHERE Products.UnitPrice > 10
--SHOWPLAN_TEXT
SET NOCOUNT ON;
USE Northwind;
GO
SET SHOWPLAN_TEXT ON;
GO
SELECT ProductName ,Products.ProductID
FROM  dbo.[Order Details]
JOIN dbo.Products
ON [Order Details].ProductID = Products.ProductID
WHERE Products.UnitPrice > 10;
GO
SET SHOWPLAN_TEXT OFF;
GO
--SHOWPLAN_ALL
SET NOCOUNT ON;
USE Northwind;
GO
SET SHOWPLAN_ALL ON;
GO
SELECT ProductName ,Products.ProductID
FROM  dbo.[Order Details]
JOIN dbo.Products
ON [Order Details].ProductID = Products.ProductID
WHERE Products.UnitPrice > 10;
GO
SET SHOWPLAN_ALL OFF;
GO

--STATISTICS XML
SET NOCOUNT ON;
USE Northwind;
GO
SET STATISTICS XML ON;
GO
SELECT ProductName ,Products.ProductID
FROM  dbo.[Order Details]
JOIN dbo.Products
ON [Order Details].ProductID = Products.ProductID
WHERE Products.UnitPrice > 10;
GO
SET STATISTICS XML OFF;
GO

--SHOWPLAN_XML
SET NOCOUNT ON;
USE Northwind;
GO
SET SHOWPLAN_XML ON;
GO
SELECT ProductName ,Products.ProductID
FROM  dbo.[Order Details]
JOIN dbo.Products
ON [Order Details].ProductID = Products.ProductID
WHERE Products.UnitPrice > 10;
GO
SET SHOWPLAN_XML OFF;
GO

--sql cache

SELECT * FROM sys.syscacheobjects

SELECT top 10  sql FROM sys.syscacheobjects

declare @tb table(id int,name varchar(50),age int) --创建表变量

insert @tb select 1,'nn',14
select * from @tb

create table #t(id int,name varchar(50),years int,nums int)--创建临时表

insert #t select 1,'nn',14,15
union all select 1,'nn',14,15
insert into #t  exec sp_gets  --可以用于存储过程或动态SQL结合

select * from #t
drop table #t --删除临时表

--1、说明：复制表(只复制结构,源表名：a 新表名：b) (Access可用)
--法一：
select * into b from dbo.Orders where 1<>1

select * from b

drop table b

--法二：
select top 0 * into bTest from dbo.Orders

select * from  bTest

drop table bTest