mysql 执行计划

执行计划：一条sql 语句在没有执行之前，先把需要的资源都计划好，例如：CPU、内存资源的分配预计，就形成成就成为“执行计划”
目前：只有“查询sql”语句支持做执行计划

无索引的执行情况

possible_keys: 可能用到的索引
rows: 收到关联查询的记录条数
key: 实际用到的索引
无索引的情况关联记录是 15547

mysql> show create table t_user; 
+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table  | Create Table                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t_user | CREATE TABLE `t_user` (
  `id` bigint(40) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) DEFAULT NULL COMMENT '???',
  `password` varchar(255) DEFAULT NULL COMMENT '????',
  `phone` varchar(30) DEFAULT NULL COMMENT '???',
  `nickname` varchar(255) DEFAULT NULL COMMENT '??',
  `realname` varchar(255) DEFAULT NULL COMMENT '????',
  `email` varchar(255) DEFAULT NULL COMMENT '??',
  `wx` varchar(255) DEFAULT NULL COMMENT '???',
  `qq` varchar(255) DEFAULT NULL COMMENT 'qq?',
  `logo` varchar(255) DEFAULT NULL COMMENT '????',
  `type` varchar(255) DEFAULT NULL COMMENT '??????????',
  `is_enable` bit(1) DEFAULT b'1' COMMENT '????',
  `is_lock` bit(1) DEFAULT b'0' COMMENT '????',
  `is_delete` bit(1) DEFAULT b'0' COMMENT '?????',
  `create_by` varchar(255) DEFAULT NULL COMMENT '???',
  `update_by` varchar(255) DEFAULT NULL COMMENT '???',
  `create_date` datetime DEFAULT NULL COMMENT '????',
  `update_date` datetime DEFAULT NULL COMMENT '????',
  `invitation_code` varchar(255) DEFAULT NULL COMMENT '???',
  `is_subscribe` bit(1) DEFAULT b'0' COMMENT '???????',
  `wallet_address` varchar(255) DEFAULT NULL COMMENT '????',
  `g_user_id` int(11) DEFAULT NULL COMMENT '?????ID',
  `calculate` int(11) DEFAULT '0' COMMENT '??????????',
  `wallet_password` varchar(255) DEFAULT NULL COMMENT '????',
  `inviter_user_id` bigint(255) DEFAULT NULL COMMENT '???ID',
  `last_activity_date` datetime DEFAULT NULL COMMENT '??????',
  `inviter_count` int(11) DEFAULT '0' COMMENT '????',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=17106 DEFAULT CHARSET=utf8 COMMENT='?????' |
+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> explain select * from t_user where t_user.phone='13270810272' \G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: t_user
   partitions: NULL
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 15547
     filtered: 10.00
        Extra: Using where
1 row in set, 1 warning (0.00 sec)

2.有索引的情况

关联记录里只有100，并且用到了索引phone

mysql> use five 
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show create  table t_user;
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table  | Create Table                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t_user | CREATE TABLE `t_user` (
  `id` bigint(40) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) DEFAULT NULL COMMENT '???',
  `password` varchar(255) DEFAULT NULL COMMENT '????',
  `phone` varchar(30) DEFAULT NULL COMMENT '???',
  `nickname` varchar(255) DEFAULT NULL COMMENT '??',
  `realname` varchar(255) DEFAULT NULL COMMENT '????',
  `email` varchar(255) DEFAULT NULL COMMENT '??',
  `wx` varchar(255) DEFAULT NULL COMMENT '???',
  `qq` varchar(255) DEFAULT NULL COMMENT 'qq?',
  `logo` varchar(255) DEFAULT NULL COMMENT '????',
  `type` varchar(255) DEFAULT NULL COMMENT '??????????',
  `is_enable` bit(1) DEFAULT b'1' COMMENT '????',
  `is_lock` bit(1) DEFAULT b'0' COMMENT '????',
  `is_delete` bit(1) DEFAULT b'0' COMMENT '?????',
  `create_by` varchar(255) DEFAULT NULL COMMENT '???',
  `update_by` varchar(255) DEFAULT NULL COMMENT '???',
  `create_date` datetime DEFAULT NULL COMMENT '????',
  `update_date` datetime DEFAULT NULL COMMENT '????',
  `invitation_code` varchar(255) DEFAULT NULL COMMENT '???',
  `is_subscribe` bit(1) DEFAULT b'0' COMMENT '???????',
  `wallet_address` varchar(255) DEFAULT NULL COMMENT '????',
  `g_user_id` int(11) DEFAULT NULL COMMENT '?????ID',
  `calculate` int(11) DEFAULT '0' COMMENT '??????????',
  `wallet_password` varchar(255) DEFAULT NULL COMMENT '????',
  `inviter_user_id` bigint(255) DEFAULT NULL COMMENT '???ID',
  `last_activity_date` datetime DEFAULT NULL COMMENT '??????',
  `inviter_count` int(11) DEFAULT '0' COMMENT '????',
  PRIMARY KEY (`id`),
  UNIQUE KEY `phone` (`phone`) USING BTREE,
  KEY `inviter_user_id` (`inviter_user_id`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=27019 DEFAULT CHARSET=utf8 COMMENT='?????' |
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> explain select * from t_user where t_user.phone='13270810272' \G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: t_user
   partitions: NULL
         type: const
possible_keys: phone
          key: phone
      key_len: 93
          ref: const
         rows: 1
     filtered: 100.00
        Extra: NULL
1 row in set, 1 warning (0.00 sec)

无索引的执行情况

2.有索引的情况

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