文章目录
1、or连接的条件
1.1、展示 tb_user 索引
mysql> show index from tb_user;
+---------+------------+----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
+---------+------------+----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| tb_user | 0 | PRIMARY | 1 | id | A | 24 | NULL | NULL | | BTREE | | | YES | NULL |
| tb_user | 0 | idx_user_phone | 1 | phone | A | 24 | NULL | NULL | | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_name | 1 | name | A | 24 | NULL | NULL | | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_pro_age_sta | 1 | profession | A | 16 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_pro_age_sta | 2 | age | A | 22 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_pro_age_sta | 3 | status | A | 24 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_email | 1 | email | A | 24 | NULL | NULL | YES | BTREE | | | YES | NULL |
+---------+------------+----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
7 rows in set (0.01 sec)
mysql>
1.2、查询 id=10 or age=23
mysql> select * from tb_user where id=10 or age=23;
+----+--------+-------------+-------------------+----------------------+------+--------+--------+---------------------+
| id | name | phone | email | profession | age | gender | status | createtime |
+----+--------+-------------+-------------------+----------------------+------+--------+--------+---------------------+
| 1 | 吕布 | 17799990000 | lvbu666@163.com | 软件工程 | 23 | 1 | 6 | 2001-02-02 00:00:00 |
| 5 | 花木兰 | 17799990004 | 19980729@sina.com | 软件工程 | 23 | 2 | 1 | 2001-04-22 00:00:00 |
| 10 | 白起 | 17799990009 | baiqi666@sina.com | 机械工程及其自动
化 | 27 | 1 | 2 | 2001-08-16 00:00:00 |
+----+--------+-------------+-------------------+----------------------+------+--------+--------+---------------------+
3 rows in set (0.00 sec)
mysql>
1.3、执行计划 id=10 or age=23
mysql> explain select * from tb_user where id=10 or age=23;
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
| 1 | SIMPLE | tb_user | NULL | ALL | PRIMARY | NULL | NULL | NULL | 24 | 13.75 | Using where |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
mysql>
1.4、给 age 创建 索引
mysql> create index idx_user_age on tb_user(age);
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> show index from tb_user;
+---------+------------+----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
+---------+------------+----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| tb_user | 0 | PRIMARY | 1 | id | A | 24 | NULL | NULL | | BTREE | | | YES | NULL |
| tb_user | 0 | idx_user_phone | 1 | phone | A | 24 | NULL | NULL | | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_name | 1 | name | A | 24 | NULL | NULL | | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_pro_age_sta | 1 | profession | A | 16 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_pro_age_sta | 2 | age | A | 22 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_pro_age_sta | 3 | status | A | 24 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_email | 1 | email | A | 24 | NULL | NULL | YES | BTREE | | | YES | NULL |
| tb_user | 1 | idx_user_age | 1 | age | A | 19 | NULL | NULL | YES | BTREE | | | YES | NULL |
+---------+------------+----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
8 rows in set (0.01 sec)
mysql>
1.4、执行计划 phone=‘17799990004’ or age=23
mysql> explain select * from tb_user where phone='17799990004' or age=23;
+----+-------------+---------+------------+-------------+-----------------------------+-----------------------------+---------+------+------+----------+-------------------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+-------------+-----------------------------+-----------------------------+---------+------+------+----------+-------------------------------------------------------+
| 1 | SIMPLE | tb_user | NULL | index_merge | idx_user_phone,idx_user_age | idx_user_phone,idx_user_age | 46,2 | NULL | 3 | 100.00 | Using union(idx_user_phone,idx_user_age); Using where |
+----+-------------+---------+------------+-------------+-----------------------------+-----------------------------+---------+------+------+----------+-------------------------------------------------------+
1 row in set, 1 warning (0.00 sec)
mysql>
2、数据分布影响
2.1、查询 tb_user
mysql> select * from tb_user;
+----+--------+-------------+-----------------------+----------------------+------+--------+--------+---------------------+
| id | name | phone | email | profession | age | gender | status | createtime |
+----+--------+-------------+-----------------------+----------------------+------+--------+--------+---------------------+
| 1 | 吕布 | 17799990000 | lvbu666@163.com | 软件工程 | 23 | 1 | 6 | 2001-02-02 00:00:00 |
| 2 | 曹操 | 17799990001 | caocao666@qq.com | 通讯工程 | 33 | 1 | 0 | 2001-03-05 00:00:00 |
| 3 | 赵云 | 17799990002 | 17799990@139.com | 英语 | 34 | 1 | 2 | 2002-03-02 00:00:00 |
| 4 | 孙悟空 | 17799990003 | 17799990@sina.com | 工程造价 | 54 | 1 | 0 | 2001-07-02 00:00:00 |
| 5 | 花木兰 | 17799990004 | 19980729@sina.com | 软件工程 | 23 | 2 | 1 | 2001-04-22 00:00:00 |
| 6 | 大乔 | 17799990005 | daqiao666@sina.com | 舞蹈 | 22 | 2 | 0 | 2001-02-07 00:00:00 |
| 7 | 露娜 | 17799990006 | luna_love@sina.com | 应用数学 | 24 | 2 | 0 | 2001-02-08 00:00:00 |
| 8 | 程咬金 | 17799990007 | chengyaojin@163.com | 化工 | 38 | 1 | 5 | 2001-05-23 00:00:00 |
| 9 | 项羽 | 17799990008 | xiaoyu666@qq.com | 金属材料 | 43 | 1 | 0 | 2001-09-18 00:00:00 |
| 10 | 白起 | 17799990009 | baiqi666@sina.com | 机械工程及其自动
化 | 27 | 1 | 2 | 2001-08-16 00:00:00 |
| 11 | 韩信 | 17799990010 | hanxin520@163.com | 无机非金属材料工
程 | 27 | 1 | 0 | 2001-06-12 00:00:00 |
| 12 | 荆轲 | 17799990011 | jingke123@163.com | 会计 | 29 | 1 | 0 | 2001-05-11 00:00:00 |
| 13 | 兰陵王 | 17799990012 | lanlinwang666@126.com | 工程造价 | 44 | 1 | 1 | 2001-04-09 00:00:00 |
| 14 | 狂铁 | 17799990013 | kuangtie@sina.com | 应用数学 | 43 | 1 | 2 | 2001-04-10 00:00:00 |
| 15 | 貂蝉 | 17799990014 | 84958948374@qq.com | 软件工程 | 40 | 2 | 3 | 2001-02-12 00:00:00 |
| 16 | 妲己 | 17799990015 | 2783238293@qq.com | 软件工程 | 31 | 2 | 0 | 2001-01-30 00:00:00 |
| 17 | 芈月 | 17799990016 | xiaomin2001@sina.com | 工业经济 | 35 | 2 | 0 | 2000-05-03 00:00:00 |
| 18 | 嬴政 | 17799990017 | 8839434342@qq.com | 化工 | 38 | 1 | 1 | 2001-08-08 00:00:00 |
| 19 | 狄仁杰 | 17799990018 | jujiamlm8166@163.com | 国际贸易 | 30 | 1 | 0 | 2007-03-12 00:00:00 |
| 20 | 安琪拉 | 17799990019 | jdodm1h@126.com | 城市规划 | 51 | 2 | 0 | 2001-08-15 00:00:00 |
| 21 | 典韦 | 17799990020 | ycaunanjian@163.com | 城市规划 | 52 | 1 | 2 | 2000-04-12 00:00:00 |
| 22 | 廉颇 | 17799990021 | lianpo321@126.com | 土木工程 | 19 | 1 | 3 | 2002-07-18 00:00:00 |
| 23 | 后羿 | 17799990022 | altycj2000@139.com | 城市园林 | 20 | 1 | 0 | 2002-03-10 00:00:00 |
| 24 | 姜子牙 | 17799990023 | 37483844@qq.com | 工程造价 | 29 | 1 | 4 | 2003-05-26 00:00:00 |
+----+--------+-------------+-----------------------+----------------------+------+--------+--------+---------------------+
24 rows in set (0.00 sec)
mysql>
2.2、查询 phone >=‘17799990020’
mysql> select * from tb_user where phone >='17799990020';
+----+--------+-------------+---------------------+------------+------+--------+--------+---------------------+
| id | name | phone | email | profession | age | gender | status | createtime |
+----+--------+-------------+---------------------+------------+------+--------+--------+---------------------+
| 21 | 典韦 | 17799990020 | ycaunanjian@163.com | 城市规划 | 52 | 1 | 2 | 2000-04-12 00:00:00 |
| 22 | 廉颇 | 17799990021 | lianpo321@126.com | 土木工程 | 19 | 1 | 3 | 2002-07-18 00:00:00 |
| 23 | 后羿 | 17799990022 | altycj2000@139.com | 城市园林 | 20 | 1 | 0 | 2002-03-10 00:00:00 |
| 24 | 姜子牙 | 17799990023 | 37483844@qq.com | 工程造价 | 29 | 1 | 4 | 2003-05-26 00:00:00 |
+----+--------+-------------+---------------------+------------+------+--------+--------+---------------------+
4 rows in set (0.00 sec)
mysql>
2.3、执行计划 phone >=‘17799990020’
mysql> explain select * from tb_user where phone >='17799990020';
+----+-------------+---------+------------+-------+----------------+----------------+---------+------+------+----------+-----------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+-------+----------------+----------------+---------+------+------+----------+-----------------------+
| 1 | SIMPLE | tb_user | NULL | range | idx_user_phone | idx_user_phone | 46 | NULL | 4 | 100.00 | Using index condition |
+----+-------------+---------+------------+-------+----------------+----------------+---------+------+------+----------+-----------------------+
1 row in set, 1 warning (0.00 sec)
mysql>
2.4、执行计划 phone >=‘17799990000’
mysql> explain select * from tb_user where phone >='17799990000';
+----+-------------+---------+------------+------+----------------+------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+------+----------------+------+---------+------+------+----------+-------------+
| 1 | SIMPLE | tb_user | NULL | ALL | idx_user_phone | NULL | NULL | NULL | 24 | 100.00 | Using where |
+----+-------------+---------+------------+------+----------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
2.5、执行计划 phone >=‘17799990010’
mysql> explain select * from tb_user where phone >='17799990010';
+----+-------------+---------+------------+------+----------------+------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+------+----------------+------+---------+------+------+----------+-------------+
| 1 | SIMPLE | tb_user | NULL | ALL | idx_user_phone | NULL | NULL | NULL | 24 | 58.33 | Using where |
+----+-------------+---------+------------+------+----------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
mysql>
2.6、执行计划 phone >=‘17799990013’
mysql> explain select * from tb_user where phone >='17799990013';
+----+-------------+---------+------------+-------+----------------+----------------+---------+------+------+----------+-----------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+-------+----------------+----------------+---------+------+------+----------+-----------------------+
| 1 | SIMPLE | tb_user | NULL | range | idx_user_phone | idx_user_phone | 46 | NULL | 11 | 100.00 | Using index condition |
+----+-------------+---------+------------+-------+----------------+----------------+---------+------+------+----------+-----------------------+
1 row in set, 1 warning (0.00 sec)
mysql>
2.7、执行计划 profession is null
mysql> explain select * from tb_user where profession is null;
+----+-------------+---------+------------+------+----------------------+----------------------+---------+-------+------+----------+-----------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+------+----------------------+----------------------+---------+-------+------+----------+-----------------------+
| 1 | SIMPLE | tb_user | NULL | ref | idx_user_pro_age_sta | idx_user_pro_age_sta | 47 | const | 1 | 100.00 | Using index condition |
+----+-------------+---------+------------+------+----------------------+----------------------+---------+-------+------+----------+-----------------------+
1 row in set, 1 warning (0.00 sec)
mysql>
2.8、执行计划 profession is not null
mysql> explain select * from tb_user where profession is not null;
+----+-------------+---------+------------+------+----------------------+------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+------+----------------------+------+---------+------+------+----------+-------------+
| 1 | SIMPLE | tb_user | NULL | ALL | idx_user_pro_age_sta | NULL | NULL | NULL | 24 | 100.00 | Using where |
+----+-------------+---------+------------+------+----------------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
mysql>
2.9、修改全表 profession=null
mysql> update tb_user set profession=null;
Query OK, 24 rows affected (0.01 sec)
Rows matched: 24 Changed: 24 Warnings: 0
mysql> select * from tb_user;
+----+--------+-------------+-----------------------+------------+------+--------+--------+---------------------+
| id | name | phone | email | profession | age | gender | status | createtime |
+----+--------+-------------+-----------------------+------------+------+--------+--------+---------------------+
| 1 | 吕布 | 17799990000 | lvbu666@163.com | NULL | 23 | 1 | 6 | 2001-02-02 00:00:00 |
| 2 | 曹操 | 17799990001 | caocao666@qq.com | NULL | 33 | 1 | 0 | 2001-03-05 00:00:00 |
| 3 | 赵云 | 17799990002 | 17799990@139.com | NULL | 34 | 1 | 2 | 2002-03-02 00:00:00 |
| 4 | 孙悟空 | 17799990003 | 17799990@sina.com | NULL | 54 | 1 | 0 | 2001-07-02 00:00:00 |
| 5 | 花木兰 | 17799990004 | 19980729@sina.com | NULL | 23 | 2 | 1 | 2001-04-22 00:00:00 |
| 6 | 大乔 | 17799990005 | daqiao666@sina.com | NULL | 22 | 2 | 0 | 2001-02-07 00:00:00 |
| 7 | 露娜 | 17799990006 | luna_love@sina.com | NULL | 24 | 2 | 0 | 2001-02-08 00:00:00 |
| 8 | 程咬金 | 17799990007 | chengyaojin@163.com | NULL | 38 | 1 | 5 | 2001-05-23 00:00:00 |
| 9 | 项羽 | 17799990008 | xiaoyu666@qq.com | NULL | 43 | 1 | 0 | 2001-09-18 00:00:00 |
| 10 | 白起 | 17799990009 | baiqi666@sina.com | NULL | 27 | 1 | 2 | 2001-08-16 00:00:00 |
| 11 | 韩信 | 17799990010 | hanxin520@163.com | NULL | 27 | 1 | 0 | 2001-06-12 00:00:00 |
| 12 | 荆轲 | 17799990011 | jingke123@163.com | NULL | 29 | 1 | 0 | 2001-05-11 00:00:00 |
| 13 | 兰陵王 | 17799990012 | lanlinwang666@126.com | NULL | 44 | 1 | 1 | 2001-04-09 00:00:00 |
| 14 | 狂铁 | 17799990013 | kuangtie@sina.com | NULL | 43 | 1 | 2 | 2001-04-10 00:00:00 |
| 15 | 貂蝉 | 17799990014 | 84958948374@qq.com | NULL | 40 | 2 | 3 | 2001-02-12 00:00:00 |
| 16 | 妲己 | 17799990015 | 2783238293@qq.com | NULL | 31 | 2 | 0 | 2001-01-30 00:00:00 |
| 17 | 芈月 | 17799990016 | xiaomin2001@sina.com | NULL | 35 | 2 | 0 | 2000-05-03 00:00:00 |
| 18 | 嬴政 | 17799990017 | 8839434342@qq.com | NULL | 38 | 1 | 1 | 2001-08-08 00:00:00 |
| 19 | 狄仁杰 | 17799990018 | jujiamlm8166@163.com | NULL | 30 | 1 | 0 | 2007-03-12 00:00:00 |
| 20 | 安琪拉 | 17799990019 | jdodm1h@126.com | NULL | 51 | 2 | 0 | 2001-08-15 00:00:00 |
| 21 | 典韦 | 17799990020 | ycaunanjian@163.com | NULL | 52 | 1 | 2 | 2000-04-12 00:00:00 |
| 22 | 廉颇 | 17799990021 | lianpo321@126.com | NULL | 19 | 1 | 3 | 2002-07-18 00:00:00 |
| 23 | 后羿 | 17799990022 | altycj2000@139.com | NULL | 20 | 1 | 0 | 2002-03-10 00:00:00 |
| 24 | 姜子牙 | 17799990023 | 37483844@qq.com | NULL | 29 | 1 | 4 | 2003-05-26 00:00:00 |
+----+--------+-------------+-----------------------+------------+------+--------+--------+---------------------+
24 rows in set (0.00 sec)
mysql>
2.10、执行计划 profession is null
mysql> explain select * from tb_user where profession is null;
+----+-------------+---------+------------+------+----------------------+------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+------+----------------------+------+---------+------+------+----------+-------------+
| 1 | SIMPLE | tb_user | NULL | ALL | idx_user_pro_age_sta | NULL | NULL | NULL | 24 | 100.00 | Using where |
+----+-------------+---------+------------+------+----------------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
mysql>
2.11、执行计划 profession is not null
mysql> explain select * from tb_user where profession is not null;
+----+-------------+---------+------------+-------+----------------------+----------------------+---------+------+------+----------+-----------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------+------------+-------+----------------------+----------------------+---------+------+------+----------+-----------------------+
| 1 | SIMPLE | tb_user | NULL | range | idx_user_pro_age_sta | idx_user_pro_age_sta | 47 | NULL | 1 | 100.00 | Using index condition |
+----+-------------+---------+------------+-------+----------------------+----------------------+---------+------+------+----------+-----------------------+
1 row in set, 1 warning (0.00 sec)
mysql>
