1、现在有如下流程：A->B->C->D->E->F，要求根据输入的参数从制定的流程执行下去 

"""
File: 01流程执行.py
Author: chde_wang
Date: 2020-08-16 18：51：35
Description:将输入存储到列表中，方便判断下一输入是否为之前的第二阶段，当前一阶段满足且输入为F时，输入结束
"""
import sys
process_list = ['A', 'B', 'C', 'D', 'E', 'F']
input_list = []
while True:print("若要退出请按quit！")input_char = input("请输入流程：")if input_char == 'quit':sys.exit()else:if input_char in process_list:for char_name in input_char:if char_name == 'A':input_list.append(char_name)print("下一流程为B")elif char_name == 'B' and input_list[-1] == 'A':input_list.append(char_name)print("下一流程为C")elif char_name == 'C' and input_list[-1] == 'B':input_list.append(char_name)print("下一流程为D")elif char_name == 'D' and input_list[-1] == 'C':input_list.append(char_name)print("下一流程为E")elif char_name == 'E' and input_list[-1] == 'D':input_list.append(char_name)print("下一流程为F")elif char_name == 'F' and input_list[-1] == 'E':input_list.append(char_name)print("流程结束")sys.exit()else:print("输入错误！", end='')else:print("输入错误，请重新输入！若要退出请按quit！")

修改：增加input_list 不为空控制：

"""
File: 01流程执行.py
Author: chde_wang
Date: 2020-08-16 18：51：35
Description:将输入存储到列表中，方便判断下一输入是否为之前的第二阶段
"""
import sys
process_list = ['A', 'B', 'C', 'D', 'E', 'F']
input_list = []
while True:print("若要退出请按quit！")input_char = input("请输入流程：")if input_char == 'quit':sys.exit()else:if input_char in process_list:if input_char == 'A':input_list.append(input_char)print("下一流程为B")elif input_list:if input_char == 'B' and input_list[-1] == 'A':input_list.append(input_char)print("下一流程为C")elif input_char == 'C' and input_list[-1] == 'B':input_list.append(input_char)print("下一流程为D")elif input_char == 'D' and input_list[-1] == 'C':input_list.append(input_char)print("下一流程为E")elif input_char == 'E' and input_list[-1] == 'D':input_list.append(input_char)print("下一流程为F")elif input_char == 'F' and input_list[-1] == 'E':input_list.append(input_char)print("流程结束")sys.exit()else:print("输入错误！", end='')else:print("输入错误，请重新输入！若要退出请按quit！")

2、数据库题目：数据库记录行转列

现有数据库记录如下：

 实现方式1-静态max实现：

SELECT`Name`,max( CASE WHEN SUBJECT = '语文' THEN Score ELSE 0 END ) AS 语文,max( CASE WHEN SUBJECT = '数学' THEN Score ELSE 0 END ) AS 数学,max( CASE WHEN SUBJECT = '英语' THEN Score ELSE 0 END ) AS 英语,max( CASE WHEN SUBJECT = '生物' THEN Score ELSE 0 END ) AS 生物 
FROMtest_a 
GROUP BYNAME;

实现方式2-静态sum实现：

SELECT`Name`,sum( CASE WHEN SUBJECT = '语文' THEN Score ELSE 0 END ) AS 语文,sum( CASE WHEN SUBJECT = '数学' THEN Score ELSE 0 END ) AS 数学,sum( CASE WHEN SUBJECT = '英语' THEN Score ELSE 0 END ) AS 英语,sum( CASE WHEN SUBJECT = '生物' THEN Score ELSE 0 END ) AS 生物 
FROMtest_a 
GROUP BYNAME;

实现方式3-动态实现：

SET @sql = NULL;
SELECTGROUP_CONCAT( DISTINCT CONCAT( 'MAX(IF(a.Subject = ''', a.Subject, ''',a.Score, 0)) AS ''', a.Subject, '''' ) ) INTO @sql
FROMmysql.test_a a;SET @sql = CONCAT('Select Name,', @sql, 'From test_a a GROUP BY a.Name');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

注：前后test_a 的别名必须一致，否则出错。

参考自https://blog.csdn.net/wqc19920906/article/details/79791322?utm_medium=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromMachineLearnPai2-1.nonecase&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromMachineLearnPai2-1.nonecase