如何取集合的并集？

# 定义两个集合
set1 = {1, 2, 3, 4}
set2 = {3, 4, 5, 6}

# 计算并集
union_set = set1.union(set2)

print(union_set)  # 输出: {1, 2, 3, 4, 5, 6}

-- 创建两个表
CREATE TABLE table1 (id INT);
CREATE TABLE table2 (id INT);

-- 插入数据
INSERT INTO table1 (id) VALUES (1), (2), (3), (4);
INSERT INTO table2 (id) VALUES (3), (4), (5), (6);

-- 查询并集
SELECT id FROM table1 UNION SELECT id FROM table2;

# 确保元素唯一
set1 = {1, 2, 3, 4}
set2 = {3, 4, 5, 6}

union_set = set1.union(set2)
print(union_set)  # 输出: {1, 2, 3, 4, 5, 6}

# 使用高效的集合操作库
import pandas as pd

df1 = pd.DataFrame({'id': [1, 2, 3, 4]})
df2 = pd.DataFrame({'id': [3, 4, 5, 6]})

union_df = pd.concat([df1, df2]).drop_duplicates()
print(union_df)  # 输出:    id
                #       0  1
                #       1  2
                #       2  3
                #       3  4
                #       4  5
                #       5  6