python中的mysql数据库LIKE操作符详解

python中的mysql数据库LIKE操作符详解
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 | 188******** | Hangzhou |
| 4 | java | 177******** | Hangzhou |
| 5 | php | 155******** | Hangzhou |
| 6 | c# | 177******** | 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 | 188******** | Hangzhou |
| 4 | java | 177******** | Hangzhou |
| 5 | php | 155******** | Hangzhou |
| 6 | c# | 177******** | 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': '188********', 'address': 'Hangzhou'}
{'id': 4, 'name': 'java', 'mobile': '177********', 'address': 'Hangzhou'}
{'id': 5, 'name': 'php', 'mobile': '155********', 'address': 'Hangzhou'}
{'id': 6, 'name': 'c#', 'mobile': '177********', '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': '177********', 'address': '浙江杭州'}
{'id': 9, 'name': '111', 'mobile': '188********', 'address': '浙江杭州'}
Process finished with exit code 0
⾄此，使⽤LIKE操作符查询完毕...
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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