Python MySQL - mysql-connector 驱动-4

where 条件语句

如果我们要读取指定条件的数据，可以使用 where 语句：

demo_mysql_test.py

读取 name 字段为 RUNOOB 的记录：

import mysql.connectormydb = mysql.connector.connect(host="localhost",user="root",passwd="123456",database="runoob_db"
)
mycursor = mydb.cursor()sql = "SELECT * FROM sites WHERE name ='RUNOOB'"mycursor.execute(sql)myresult = mycursor.fetchall()for x in myresult:print(x)

执行代码，输出结果为：

(1,'RUNOOB','https://www.runoob.com')

也可以使用通配符 %：

demo_mysql_test.py

import mysql.connectormydb = mysql.connector.connect(host="localhost",user="root",passwd="123456",database="runoob_db"
)
mycursor = mydb.cursor()sql = "SELECT * FROM sites WHERE url LIKE '%oo%'"mycursor.execute(sql)myresult = mycursor.fetchall()for x in myresult:print(x)

执行代码，输出结果为：

(1,'RUNOOB','https://www.runoob.com')
(2,'Google','https://www.google.com')

为了防止数据库查询发生 SQL 注入的攻击，我们可以使用 %s 占位符来转义查询的条件：

demo_mysql_test.py

import mysql.connectormydb = mysql.connector.connect(host="localhost",user="root",passwd="123456",database="runoob_db"
)
mycursor = mydb.cursor()sql = "SELECT * FROM sites WHERE name = %s"
na = ("RUNOOB", )mycursor.execute(sql, na)myresult = mycursor.fetchall()for x in myresult:print(x)

排序

查询结果排序可以使用 ORDER BY 语句，默认的排序方式为升序，关键字为 ASC ，如果要设置降序排序，可以设置关键字 DESC 。

demo_mysql_test.py

按 name 字段字母的升序排序：

import mysql.connectormydb = mysql.connector.connect(host="localhost",user="root",passwd="123456",database="runoob_db"
)
mycursor = mydb.cursor()sql = "SELECT * FROM sites ORDER BY name"mycursor.execute(sql)myresult = mycursor.fetchall()for x in myresult:print(x)

执行代码，输出结果为：

(3,'Github','https://www.github.com')
(2,'Google','https://www.google.com')
(1,'RUNOOB','https://www.runoob.com')
(5,'stackoverflow','https://www.stackoverflow.com/')
(4,'Taobao','https://www.taobao.com')
(6,'Zhihu','https://www.zhihu.com')

降序排序实例：

demo_mysql_test.py

按 name 字段字母的降序排序：

import mysql.connectormydb = mysql.connector.connect(host="localhost",user="root",passwd="123456",database="runoob_db"
)
mycursor = mydb.cursor()sql = "SELECT * FROM sites ORDER BY name DESC"mycursor.execute(sql)myresult = mycursor.fetchall()for x in myresult:print(x)

执行代码，输出结果为：

(6,'Zhihu','https://www.zhihu.com')
(4,'Taobao','https://www.taobao.com')
(5,'stackoverflow','https://www.stackoverflow.com/')
(1,'RUNOOB','https://www.runoob.com')
(2,'Google','https://www.google.com')
(3,'Github','https://www.github.com')