摘要：
1．如果索引了多列，遵守最左前缀法则。所谓最左前缀，指的是查询从索引的最左前列开始，并且不跳过索引中的列。mysql> explain select uid, fuid, name from ptb where uid=1378109017;+----+-------------+-------+------+---------------+----------+---------+-------+------+-------+| id | select_type | table | type | possible_keys | key | key_len | ref | rows | 阅读全文
