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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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