MySQL - 模糊搜索 LIKE BINARY 和 LIKE

Posted 2021-11-03 程序员牧码

mysql 模糊搜索

MySQL 模糊搜索： LIKE BINARY 是区分大小写的； LIKE 是否区分大小写，取决于表的 COLLATE，如果 COLLATE=utf8_bin 即二进制形式就是区分大小写的，否则是不区分的。

在 ORM 中过滤的时候会写 xxx.objects.filter(name__contains=‘sxn’) 和 xxx.objects.filter(name__icontains=‘sxn’) 转成的 SQL分别是: LIKE BINARY 和 LIKE

(drf_poc_env) root@robert-Ubuntu:/media/sf_WorkSpace/drf_poc# python manage.py shell
Python 2.7.12 (default, Nov 12 2018, 14:36:49) 
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> 
>>> from app01.models import UserInfo
>>> 
>>> UserInfo.objects.filter(username__contains='SXN')  ----用的是  LIKE BINARY
DEBUG 2020-04-01 11:01:07,836 4942 140546619713280 utils 90 Line (0.001) 
SELECT `app01_userinfo`.`id`, `app01_userinfo`.`user_type`, `app01_userinfo`.`username`, `app01_userinfo`.`password` 
FROM `app01_userinfo` 
WHERE `app01_userinfo`.`username` LIKE BINARY '%SXN%' LIMIT 21; args=(u'%SXN%',)
<QuerySet []>
>>> 
>>> 
>>> 
>>> UserInfo.objects.filter(username__icontains='SXN')  ----用的是  LIKE 
DEBUG 2020-04-01 11:01:25,360 4942 140546619713280 utils 90 Line (0.001) 
SELECT `app01_userinfo`.`id`, `app01_userinfo`.`user_type`, `app01_userinfo`.`username`, `app01_userinfo`.`password` 
FROM `app01_userinfo` 
WHERE `app01_userinfo`.`username` LIKE '%SXN%' LIMIT 21; args=(u'%SXN%',)
<QuerySet [<UserInfo: UserInfo object>]>
>>> 
>>> 
mysql> show create table app01_userinfo \\G     -----注意表的 COLLATE 用是默认值，并不是COLLATE=utf8_bin 
*************************** 1. row ***************************
       Table: app01_userinfo
Create Table: CREATE TABLE `app01_userinfo` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_type` int(11) NOT NULL,
  `username` varchar(32) NOT NULL,
  `password` varchar(32) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `username` (`username`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8
1 row in set (0.01 sec)
mysql> 
mysql> 
mysql> select * from app01_userinfo where username like binary '%sxn%';
+----+-----------+----------+----------+
| id | user_type | username | password |
+----+-----------+----------+----------+
|  2 |         2 | sxn      | 655      |
+----+-----------+----------+----------+
1 row in set (0.00 sec)
mysql> 
mysql> select * from app01_userinfo where username like binary '%SXN%';
Empty set (0.00 sec)
mysql> 
mysql> 
mysql> 
mysql> select * from app01_userinfo where username like '%sxn%';
+----+-----------+----------+----------+
| id | user_type | username | password |
+----+-----------+----------+----------+
|  2 |         2 | sxn      | 655      |
+----+-----------+----------+----------+
1 row in set (0.00 sec)
mysql> 
mysql> select * from app01_userinfo where username like '%SXN%';
+----+-----------+----------+----------+
| id | user_type | username | password |
+----+-----------+----------+----------+
|  2 |         2 | sxn      | 655      |
+----+-----------+----------+----------+
1 row in set (0.00 sec)

mysql> 

mysql> show create table db_work_order \\G      --------- 注意表的  COLLATE=utf8_bin 
*************************** 1. row ***************************
       Table: db_work_order
Create Table: CREATE TABLE `db_work_order` (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键',
  `order_num` varchar(64) COLLATE utf8_bin NOT NULL COMMENT '工单编号',
  `order_type` varchar(32) COLLATE utf8_bin NOT NULL COMMENT '工单类型',
  ......
  `create_time` datetime(6) NOT NULL COMMENT '创建时间',
  `update_time` datetime(6) NOT NULL COMMENT '更新时间',
  PRIMARY KEY (`id`),
  UNIQUE KEY `uqi_ordernum` (`order_num`),
  KEY `created_time` (`create_time`)
) ENGINE=InnoDB AUTO_INCREMENT=1578 DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='数据库类别的工单表'
1 row in set (0.05 sec)

mysql> 
mysql>   ------可以看到是区分大小写的------
mysql> select id, order_num  from db_work_order where order_num LIKE '%DB_change%' limit 3;
Empty set (0.01 sec)
mysql> 
mysql> select id, order_num  from db_work_order where order_num LIKE '%db_change%' limit 3;
+-----+-----------------------+
| id  | order_num             |
+-----+-----------------------+
| 392 | db_change202003030106 |
| 335 | db_change202003040029 |
|  67 | db_change202003040078 |
+-----+-----------------------+
3 rows in set (0.00 sec)
mysql> 


是不是和环境变量也有关系？这个待确定
mysql> show variables like '%lower%';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| lower_case_file_system | ON    |
| lower_case_table_names | 1     |
+------------------------+-------+
2 rows in set, 1 warning (0.00 sec)

mysql>

SQL WHERE 中的空格

mysql> show create table db_work_order \\G      --------- 注意表的  COLLATE=utf8_bin 
*************************** 1. row ***************************
       Table: db_work_order
Create Table: CREATE TABLE `db_work_order` (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键',
  `order_num` varchar(64) COLLATE utf8_bin NOT NULL COMMENT '工单编号',
  `order_type` varchar(32) COLLATE utf8_bin NOT NULL COMMENT '工单类型',
  ......
  `create_time` datetime(6) NOT NULL COMMENT '创建时间',
  `update_time` datetime(6) NOT NULL COMMENT '更新时间',
  PRIMARY KEY (`id`),
  UNIQUE KEY `uqi_ordernum` (`order_num`),
  KEY `created_time` (`create_time`)
) ENGINE=InnoDB AUTO_INCREMENT=1578 DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='数据库类别的工单表'
mysql>
mysql> select order_num, order_type, length(order_type) from db_work_order where order_type = 'cds_change_bak    ' limit 3;
+----------------------------+----------------+--------------------+
| order_num                  | order_type     | length(order_type) |
+----------------------------+----------------+--------------------+
| cds_change_bak202003050001 | cds_change_bak |                 14 |
| cds_change_bak202003050002 | cds_change_bak |                 14 |
| cds_change_bak202003060001 | cds_change_bak |                 14 |
+----------------------------+----------------+--------------------+
3 rows in set (0.00 sec)

mysql>

因为 order_type 的类型是 varchar 所以在 WHERE 中会忽略 'cds_change_bak ’ 中的空格，因为在varcahr 在存储的时候就会把后缀的空格给截断，注意前导空格不会忽略。