SQL去掉重复 sqlserver 去除重复数据



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SQL去掉重复 sqlserver 去除重复数据

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【SQL去掉重复 sqlserver 去除重复数据】废话不多说,直接干货 。
一、oracle去重
1、创建测试数据
create table test_duplicate_removal(c001 number,c002 varchar2(100));insert into test_duplicate_removal values(101, 'aa');insert into test_duplicate_removal values(102, 'aa');insert into test_duplicate_removal values(103, 'aa');insert into test_duplicate_removal values(104, 'bb');insert into test_duplicate_removal values(105, 'bb');insert into test_duplicate_removal values(106, 'cc');insert into test_duplicate_removal values(107, 'cc');insert into test_duplicate_removal values(108, 'dd');
2、使用row_number() over()函数根据C002列去重
创建一个rn列,根据C002进行分组,每个小组内再根据C001的值进行排序 。
select c001,c002, row_number()over(partition by c002 order by c001 desc) rn fromtest_duplicate_removal
通过rn筛选值为1的行,同时也就对C002进行了去重
select * from (select c001,c002, row_number()over(partition by c002 order by c001 desc) rn fromtest_duplicate_removal) t where t.rn=1
二、python的pandas模块去重方法
1、将数据库数据导出保存为CSV
2、pandas实现sql里排序函数row_number() over()功能
import pandas as pd# 读取CSV数据df = pd.read_csv('test_duplicate_removal.csv')print('打印原始数据:')print(df)# 此处等价于sql里的排序函数row_number() over()功能df['RN'] = df['C001'].groupby(df['C002']).rank()print()print('根据C002分组,根据C001组内排序:')print(df)# 去重print()print('去重,筛选RN=1的行:')print(df[df['RN'] == 1])运行结果