摘要：
以前对explain工具不是很了解，抽空学习了下。真的很强大。首先分析下两条sql带来的性能问题。开启profilingset profiling=1;34 | 0.01580100 | select sql_no_cache * from user left join user_ext on user.id = user_ext.id where user_ext.id <100 ORDER BY user_ext.id limit 1035 | 0.04485000 | select sql_no_cache * from user left join user_ext on use 阅读全文
