MySQL 连接器/Python 开发人员指南 / 第 6 章连接器/Python 教程 /
6.1 教程:使用缓冲游标提高员工工资
下面的示例脚本为 2000 年加入公司并仍在公司工作的所有员工提供了逾期已久的 15% 加薪,明天生效。
为了遍历选定的员工,我们使用缓冲游标。(缓冲游标在执行查询后获取并缓冲结果集的行;请参阅 第 10.6.1 节,“cursor.MySQLCursorBuffered 类”。)这样,就不需要在新变量中获取行。相反,游标可以用作迭代器。
笔记
这个脚本是一个例子;还有其他方法可以完成这项简单的任务。
from __future__ import print_function
from decimal import Decimal
from datetime import datetime, date, timedelta
import mysql.connector
# Connect with the MySQL Server
cnx = mysql.connector.connect(user='scott', database='employees')
# Get two buffered cursors
curA = cnx.cursor(buffered=True)
curB = cnx.cursor(buffered=True)
# Query to get employees who joined in a period defined by two dates
query = (
"SELECT s.emp_no, salary, from_date, to_date FROM employees AS e "
"LEFT JOIN salaries AS s USING (emp_no) "
"WHERE to_date = DATE('9999-01-01')"
"AND e.hire_date BETWEEN DATE(%s) AND DATE(%s)")
# UPDATE and INSERT statements for the old and new salary
update_old_salary = (
"UPDATE salaries SET to_date = %s "
"WHERE emp_no = %s AND from_date = %s")
insert_new_salary = (
"INSERT INTO salaries (emp_no, from_date, to_date, salary) "
"VALUES (%s, %s, %s, %s)")
# Select the employees getting a raise
curA.execute(query, (date(2000, 1, 1), date(2000, 12, 31)))
# Iterate through the result of curA
for (emp_no, salary, from_date, to_date) in curA:
# Update the old and insert the new salary
new_salary = int(round(salary * Decimal('1.15')))
curB.execute(update_old_salary, (tomorrow, emp_no, from_date))
curB.execute(insert_new_salary,
(emp_no, tomorrow, date(9999, 1, 1,), new_salary))
# Commit the changes
cnx.commit()
cnx.close()