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SQL中in或or与union all性能对比

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2016-05-25 16:43:271254browse

//使用or,代码如下: 
WHERE * FROM article  
WHERE article_category=2  
OR article_category=3  
ORDER BY article_id DESC  
LIMIT 5  
// 执行时间：11.0777 
 
//使用in,代码如下: 
SELECT * FROM article  
WHERE article_category IN (2,3)  
ORDER BY article_id DESC  
LIMIT 5 
 // 执行时间：11.2850 
 
//使用union all,代码如下: 
(  
SELECT * FROM article  
WHERE article_category=2  
ORDER BY article_id DESC  
LIMIT 5  
) UNION ALL (  
SELECT * FROM article  
WHERE article_category=3  
ORDER BY article_id DESC  
LIMIT 5  
)  
ORDER BY article_id DESC  
LIMIT 5  
// 执行时间：0.0261


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