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count(*) 和count(字段名)的区别_MySQL

WBOY
WBOYOriginal
2016-06-01 13:49:011357browse

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以前没有注意两者的区别，看博客园的文章，还真引起了我的注意。

数据测试：见图

sql 语句见分晓：

SELECT COUNT(*) c1 ,COUNT(ADDRESS) c2 FROM test

显而易见，count(*)统计的是结果集的总条数，count(字段名)统计的是该字段值不为null的总条数

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