sql中带in条件的查询及提高效率-木庄网络博客

2020-01-14 09:07:16 博客园-曾祥展数据库

本文摘自博客园-曾祥展，原文地址：https://www.cnblogs.com/zengxiangzhan/archive/2010/01/03/1638152.html，侵删。

ALTER PROCEDURE [dbo].[example1]
(
@booker varchar(100)
)
AS
declare @str varchar(1000) 
set @str='select * from tb_itregister where booker in(' + @booker + ')'
execute (@str)

调用：
string booker = "a,b";
        booker = booker.Replace(",", "','");
        booker = "'" + booker + "'";



 

/************************************************************
     问题描述： id值可能有数千个之多，怎么提高效率？
     例子：select * from table1 where id in (1,3,6,10,...,8000) and type = 1
 ************************************************************/

 --例如:
    SELECT *
    FROM   tb
    WHERE  id IN (1, 2, 3, 4, ........)
           AND NAME = 'best'    
     
 --1.将括号的条件做成变量
    DECLARE @str VARCHAR(4000) 
    SET @str = '1,2,3,4,5.......'
     
 --2.然后将@s拆分后插入临时表
    CREATE TABLE #t
    (
        id VARCHAR(10)
    ) 
    DECLARE @i    INT 
    DECLARE @len  INT 
    SET @i = 1 
    WHILE @i < LEN(@str + ',')
    BEGIN
        INSERT #t
        SELECT SUBSTRING(@str + ',', @i, CHARINDEX(',', @str + ',', @i) -@i)
        
        SET @i = CHARINDEX(',', @str + ',', @i) + 1
    END 

 --3利用临时表和原表进行连接取值
    SELECT k.* 
    FROM   tb k
           INNER JOIN #t p
                ON  p.id = k.id
    WHERE  NAME = 'best'