cosmic数据库圈图

Cosmic Database圈图是指在Cosmic数据库中，使用圆形图表来显示数据库中表之间的关系。它可以帮助用户了解数据库中表之间的关联关系，优化查询性能，提高数据访问效率。

实现圈图可以使用Python的matplotlib库绘制圆形图表。首先需要安装matplotlib库，可以使用pip在命令行中安装：

pip install matplotlib

接下来，我们需要先获取Cosmic数据库中所有的表及其之间的关系。可以使用以下SQL查询语句：

SELECT
    tc.table_name as table1,
    kcu.column_name as column1,
    ccu.table_name as table2,
    ccu.column_name as column2 
FROM 
    information_schema.table_constraints as tc 
    JOIN information_schema.key_column_usage as kcu
      ON tc.constraint_name = kcu.constraint_name
    JOIN information_schema.constraint_column_usage as ccu
      ON ccu.constraint_name = tc.constraint_name
WHERE 
    tc.constraint_type = 'FOREIGN KEY';

上述SQL语句可以获取所有Cosmic数据库中的外键关系，包括原表、引用表和相应的列。使用Python的pymysql库可以连接数据库，并执行SQL查询语句：

import pymysql

con = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='password', db='cosmic')

cur = con.cursor()

sql = """SELECT
    tc.table_name as table1,
    kcu.column_name as column1,
    ccu.table_name as table2,
    ccu.column_name as column2 
FROM 
    information_schema.table_constraints as tc 
    JOIN information_schema.key_column_usage as kcu
      ON tc.constraint_name = kcu.constraint_name
    JOIN information_schema.constraint_column_usage as ccu
      ON ccu.constraint_name = tc.constraint_name
WHERE 
    tc.constraint_type = 'FOREIGN KEY';"""

cur.execute(sql)

result_set = cur.fetchall()

获取所有外键关系后，需要将其转换为圆形图表的形式。可以使用Python的matplotlib库实现。以下是一个实现的示例代码：

import matplotlib.pyplot as plt
import networkx as nx

G = nx.Graph()

for res in result_set:
    table1 = res[0]
    column1 = res[1]
    table2 = res[2]
    column2 = res[3]
    G.add_edge(table1,table2)
    
pos = nx.circular_layout(G)

nx.draw_circular(G, with_labels=True, node_color='light