python中的mysql数据库LIKE操作符怎么用

LIKE 操作符用于在 WHERE 子句中搜索列中的指定模式。

语法：

SELECT column_name(s)
FROM table_name
WHERE column_name LIKE pattern

pattern这里就是放指定模板的地方，而这里就要用到“ % ”，也叫做通配符

%如果是放在条件前面，那就是查以...结尾的数据；例如：%李

%如果是放在条件后面，那就是查以...开头的数据；例如：李%

%如果是在条件前后都存在，那就是查包含的数据；例如：%李%

小知识点：

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near "%z" at line 1

1064的错误就是LIKE查询时(语法错误)，通配符处没加引号，所以才会报错...

正确展示例如："%李%"

示例1：终端运行sql且WHERE子句中使用LIKE

查询地址以Hang开头的人员信息

root@7c6316b19d80:/# mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 140
Server version: 5.6.51 MySQL Community Server (GPL)
 
mysql> mysql> select * from test_user where address like "Hang%";
+----+--------+-------------+----------+
| id | name   | mobile      | address  |
+----+--------+-------------+----------+
|  3 | python | 18856565858 | Hangzhou |
|  4 | java   | 17756565858 | Hangzhou |
|  5 | php    | 15556565858 | Hangzhou |
|  6 | c#     | 17748484142 | Hangzhou |
+----+--------+-------------+----------+
4 rows in set (0.00 sec)
mysql>

查询地址以u结尾的人员信息

mysql> select * from test_user where address like "%u";
+----+--------+-------------+----------+
| id | name   | mobile      | address  |
+----+--------+-------------+----------+
|  3 | python | 18856565858 | Hangzhou |
|  4 | java   | 17756565858 | Hangzhou |
|  5 | php    | 15556565858 | Hangzhou |
|  6 | c#     | 17748484142 | Hangzhou |
+----+--------+-------------+----------+
4 rows in set (0.00 sec)
mysql>

示例2：使用python脚本执行含LIKE的sql语句

查询地址包含z字符的人员信息

import pymysql
 
# 连接数据库
connection = pymysql.connect(host="localhost", user="root", password="123456",
                             database="testing", port=3306, charset="utf8",
                             cursorclass=pymysql.cursors.DictCursor)
 
try:
    with connection:
        with connection.cursor() as cursor:
            sql = """
                SELECT
                    *
                FROM
                    test_user
                WHERE
                    address LIKE "%z%";
            """
            cursor.execute(sql)
            result = cursor.fetchall()
            for i in result:
                print(i)
 
except pymysql.err.MySQLError as _error:
    raise _error

{"id": 3, "name": "python", "mobile": "18856565858", "address": "Hangzhou"}
{"id": 4, "name": "java", "mobile": "17756565858", "address": "Hangzhou"}
{"id": 5, "name": "php", "mobile": "15556565858", "address": "Hangzhou"}
{"id": 6, "name": "c#", "mobile": "17748484142", "address": "Hangzhou"}
 
Process finished with exit code 0

查询地址不包含z字符的人员信息

try:
    with connection:
        with connection.cursor() as cursor:
            sql = """
                SELECT
                    *
                FROM
                    test_user
                WHERE
                    address NOT LIKE "%z%";
            """
            cursor.execute(sql)
            result = cursor.fetchall()
            for i in result:
                print(i)
 
except pymysql.err.MySQLError as _error:
    raise _error

{"id": 1, "name": "张三三", "mobile": "17748484141", "address": "浙江杭州"}
{"id": 9, "name": "111", "mobile": "18847474549", "address": "浙江杭州"}
 
Process finished with exit code 0

知识点扩展：python中的mysql数据库like模糊查询

%在python中是个特殊的符号，如%s，%d分别代表了字符串占位符和数字占位符。

大家知道，mysql的模糊查询也需要用到%。

所以，可以先把需要查的字符串抽出来，再以参数方式传入。

args = "%"+subtitle+"%"
sqlQueryTitle="select count(*) from tbl_peng_article where title like "%s""%args

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