1.MySQL 模糊搜索
MySQL 模糊搜索： LIKE BINARY 是區分大小寫的； LIKE 是否區分大小寫,取決於表的 COLLATE，如果 COLLATE=utf8_bin 即二進制形式就是區分大小寫的, 否則是不區分的。
在 ORM 中過濾的時候會寫 xxx.objects.filter(name__contains=‘sxn’) 和 xxx.objects.filter(name__icontains=‘sxn’) 轉成的 SQL分別是: 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 用是默認值，並不是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 '主鍵',
`order_num` varchar(64) COLLATE utf8_bin NOT NULL COMMENT '工單編號',
`order_type` varchar(32) COLLATE utf8_bin NOT NULL COMMENT '工單類型',
......
`create_time` datetime(6) NOT NULL COMMENT '創建時間',
`update_time` datetime(6) NOT NULL COMMENT '更新時間',
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='數據庫類別的工單表'
1 row in set (0.05 sec)
mysql>
mysql> ------可以看到是區分大小寫的------
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>
是不是和環境變量也有關係？這個待確定
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>
2.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 '主鍵',
`order_num` varchar(64) COLLATE utf8_bin NOT NULL COMMENT '工單編號',
`order_type` varchar(32) COLLATE utf8_bin NOT NULL COMMENT '工單類型',
......
`create_time` datetime(6) NOT NULL COMMENT '創建時間',
`update_time` datetime(6) NOT NULL COMMENT '更新時間',
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='數據庫類別的工單表'
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>
因爲 order_type 的類型是 varchar 所以在 WHERE 中會忽略 'cds_change_bak ’ 中的空格，因爲在varcahr 在存儲的時候就會把後綴的空格給截斷，注意前導空格不會忽略。