mysql_num_rows VS COUNT 效率问题分析_php技巧
mysql_num_rows 和 count( * ) 都能统计总数,那个能好一点呢？
或者
分别什么时候用num_rows 和 count( * )呢
一个直观的对比
测试数据：
条数：139764条
数据表大小：500M
结果：
fetch_num_rows 用时：35.272329092026
count(*) 用时：0.071956872940063
如果单纯统计数量 当然是count(*)
fetch_num_rows必须遍历数据库以后才能得出 效率低于count(*)
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