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explain执行计划看过没有?其中type字段都有哪些值?分别代表什么?
The text was updated successfully, but these errors were encountered:
在日常工作中,我们的项目如果发现查询很慢了,往往会去查看MySQL的慢查询日志,找到对应的SQL; 找到这个SQL并不就此完事儿了,还会对当前SQL进行优化;使用MySQL的explain命令,将会事半功倍!
但是就目前来看,explain指令的解析都是文字,大量的文字!一点不形象、不直观、使用的时候查起来也非常麻烦,因此,我做了一张表格,供大家参考和查阅。
以下是Mysql执行计划的图解。在使用explain的时候可以参考使用。
概要描述: id:选择标识符 select_type:表示查询的类型。 table:输出结果集的表 partitions:匹配的分区 type:表示表的连接类型 possible_keys:表示查询时,可能使用的索引 key:表示实际使用的索引 key_len:索引字段的长度 ref:列与索引的比较 rows:扫描出的行数(估算的行数) filtered:按表条件过滤的行百分比 Extra:执行情况的描述和说明
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explain执行计划看过没有?其中type字段都有哪些值?分别代表什么?
The text was updated successfully, but these errors were encountered: