数据库的增删查改如何用代码实现

数据库的增删查改是数据库最常用的四种操作，通常使用 SQL 语句进行实现。下面是使用 Python 语言和 MySQL 数据库进行增删查改的示例代码：

1. 连接数据库

import mysql.connector

mydb = mysql.connector.connect(
  host="localhost",
  user="yourusername",
  password="yourpassword",
  database="mydatabase"
)

mycursor = mydb.cursor()

2. 插入数据

sql = "INSERT INTO customers (name, address) VALUES (%s, %s)"
val = ("John", "Highway 21")

mycursor.execute(sql, val)

mydb.commit()

print(mycursor.rowcount, "record inserted.")

3. 查询数据

mycursor.execute("SELECT * FROM customers")

myresult = mycursor.fetchall()

for x in myresult:
  print(x)

4. 更新数据

sql = "UPDATE customers SET address = 'Canyon 123' WHERE address = 'Highway 21'"

mycursor.execute(sql)

mydb.commit()

print(mycursor.rowcount, "record(s) affected")

5. 删除数据

sql = "DELETE FROM customers WHERE address = 'Canyon 123'"

mycursor.execute(sql)

mydb.commit()

print(mycursor.rowcount, "record(s) deleted")

以上示例代码仅供参考，实际应用中需要根据具体情况进行修改。