哪个最快?从“表"中选择SELECT SQL_CALC_FOUND_ROWS，或选择COUNT(*) [英] Which is fastest? SELECT SQL_CALC_FOUND_ROWS FROM `table`, or SELECT COUNT(*)

问题描述

当限制通常用于分页的SQL查询返回的行数时，有两种方法可确定记录总数:

When you limit the number of rows to be returned by a SQL query, usually used in paging, there are two methods to determine the total number of records:

在原始的SELECT中包含SQL_CALC_FOUND_ROWS选项，然后通过运行SELECT FOUND_ROWS()获得行的总数:

Include the SQL_CALC_FOUND_ROWS option in the original SELECT, and then get the total number of rows by running SELECT FOUND_ROWS():

SELECT SQL_CALC_FOUND_ROWS * FROM table WHERE id > 100 LIMIT 10;
SELECT FOUND_ROWS();  

方法2

正常运行查询，然后通过运行SELECT COUNT(*)

SELECT * FROM table WHERE id > 100 LIMIT 10;
SELECT COUNT(*) FROM table WHERE id > 100;  

哪种方法最好/最快?

推荐答案

这要视情况而定.请参阅有关此主题的MySQL Performance Blog帖子: http://www.mysqlperformanceblog.com/2007/08/28/to-sql_calc_found_rows-or-not-to-sql_calc_found_rows/

It depends. See the MySQL Performance Blog post on this subject: http://www.mysqlperformanceblog.com/2007/08/28/to-sql_calc_found_rows-or-not-to-sql_calc_found_rows/

快速摘要:彼得说，这取决于您的索引和其他因素.帖子中的许多评论似乎都说SQL_CALC_FOUND_ROWS几乎总是比运行两个查询慢-有时甚至慢10倍.

Just a quick summary: Peter says that it depends on your indexes and other factors. Many of the comments to the post seem to say that SQL_CALC_FOUND_ROWS is almost always slower - sometimes up to 10x slower - than running two queries.

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