SQL Server 常用分页SQL

作者:Pride+Zhou 和mssql相关  

今天无聊和朋友讨论分页,发现网上好多都是错的。网上经常查到的那个Top Not in 或者Max 大部分都不实用,很多都忽略了Order和性能问题。为此上网查了查,顺带把2000和2012版本的也补上了。

先说说网上常见SQL的错误或者说局限问题

select top 10 * 
from table1
where id not in(
    select top 开始的位置 id 
    from table1)

这样的确是可以取到分页数据,但是这是默认排序的,如果要按其中一列排序呢?那order by 加在哪里呢?里外都加,显然不行,外面的Order不起作用,只能嵌套,Oh my god,编程三个Select了,这效率。

为了好用效率高,总体思路还是老老实实的用RowNumber解决,但是SQL2000没有RowNumber,其实我们可以通过临时表自增列搞定,不多说,上例子。

 

SQL 2000 用临时表解决,通过在临时表中增加自增列解决RowNumber。

DECLARE @Start INT
DECLARE @End INT
SELECT @Start = 14000,@End = 14050


CREATE TABLE #employees (RowNumber INT IDENTITY(1,1),
LastName VARCHAR(100),FirstName VARCHAR(100),
EmailAddress VARCHAR(100))


INSERT INTO #employees (LastName, FirstName, EmailAddress)
SELECT LastName, FirstName, EmailAddress 
FROM Employee 
ORDER BY LastName, FirstName, EmailAddress
SELECT LastName, FirstName, EmailAddress 
FROM #employees
WHERE RowNumber > @Start AND RowNumber <= @End


DROP TABLE #employees


GO

  


SQL 2005/2008 由于支持了Row_Number于是通过派生表的方式解决(两个嵌套)

DECLARE @Start INT
DECLARE @End INT
SELECT @Start = 14000,@End = 14050


SELECT LastName, FirstName, EmailAddress
FROM (SELECT LastName, FirstName, EmailAddress,
ROW_NUMBER() OVER (ORDER BY LastName, FirstName, EmailAddress) AS RowNumber
FROM Employee) EmployeePage
WHERE RowNumber > @Start AND RowNumber <= @End
ORDER BY LastName, FirstName, EmailAddress
GO

  


SQL 2005/2008 或者用CTE的方式实现,和派生表一样,就是好看点,执行计划都一样。

DECLARE @Start INT
DECLARE @End INT
SELECT @Start = 14000,@End = 14050;


WITH EmployeePage AS
(SELECT LastName, FirstName, EmailAddress,
ROW_NUMBER() OVER (ORDER BY LastName, FirstName, EmailAddress) AS RowNumber
FROM Employee)
SELECT LastName, FirstName, EmailAddress
FROM EmployeePage
WHERE RowNumber > @Start AND RowNumber <= @End
ORDER BY LastName, FirstName, EmailAddress
GO

  


SQL SERVER 2012 比较给力支持了OFFSET,于是一个Select结束战斗

SELECT LastName, FirstName, EmailAddress
FROM Employee
ORDER BY LastName, FirstName, EmailAddress
OFFSET 14000 ROWS
FETCH NEXT 50 ROWS ONLY;

  

 

最后说下,根据老外的文章,在2012里,如果前面加上TOP(50),那么执行计划就会少读很多行数据(读的精准了),提高性能。但是鉴于本人手头没2012也无法测试。至少在2008R2上加不加TOP执行计划都一样。

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