#接口返回值 list1 = ['张三', '李四', '王五', '老二'] #数据库返回值 list2 = ['张三', '李四', '老二', '王七'] a = [x for x in list1 if x in list2] #两个列表表都存在 b = [y for y in (list1 + list2) if y not in a] #两个列表中的不同元素 print('a的值为:',a) print('b的值为:',b) c = [x for x in list1 if x no
(一)单个字段 1.查找表中多余的重复记录,根据(question_title)字段来判断 代码如下 复制代码 select * from questions where question_title in (select question_title from people group by question_title having count(question_title) > 1) 2.删除表中多余的重复记录,根据(question_title)字段来判断,只留有一个记录 代码如下 复制
删除表中重复数据,留下ID比较小的行 delete from 表 where [重复字段] in (select [重复字段] from 表 group by 字段 having count([字段]) > 1) and ID not in (select min(ID) from [表] group by [字段] having count([字段])> 1)
1.针对PostgreSQL数据库表的去重复方法基本有三种,这是在网上查找的方法,在附录1给出.但是这些方法对GreenPlum来说都不管用. 2.数据表分布在不同的节点上,每个节点的ctid是唯一的,但是不同的节点就有ctid重复的可能,因此GreenPlum必须借助gp_segment_id来进行去重复处理. 3.在网上找到了一个相对繁琐的方法,在附录2给出: 4.最终的方法是: delete from test where (gp_segment_id, ctid) not in (sel
以下举例是查询相同数据,否则则相反 方法一: select * from A as x,B as y where x.a1=y.b1 and x.a2=y.b2 and x.a3=y.b3 方法二: select * from tb INTERSECT --UNION select * from dataname.dbo.tb
delete from test where id in (select id from (select max(id) as id,count(text) as count from test group by text having count >1 order by count desc) as tab ) 测试代码 INSERT IGNORE INTO test_1(text,text2) values ('1111','22222'); INSERT IGNORE INTO t
为了性能考虑,在阅读之前提醒大家,如果有子查询,子查询查询到的数据最好不要超过总数据量的30%. 查询有重复数据的记录 select * from F group by a,b,c,d having count(*)>1 select distinct * into #Tmp from tableName drop table tableName select * into tableName from #Tmp drop table #Tmp SQL删除重复数据方法 例如: id name
1.查询表中重复数据.select * from peoplewhere peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)2.删除表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断,只留有rowid最小的记录delete from people where peopleId in (select peopleId
Python实现MapReduce 下面使用mapreduce模式实现了一个简单的统计日志中单词出现次数的程序: from functools import reduce from multiprocessing import Pool from collections import Counter def read_inputs(file): for line in file: line = line.strip() yield line.split() def count(file_name
查询同一个表中某一字段值相同的记录 select * from 表名 where 字段 in(select 字段 from 表名 group by 字段 having count(1)>1) select * from 表名 awhere exists (select 1 from 表名 where 字段=a.字段 and 主键<> a.主键) 用select top 查询出多条记录的解决 这个问题在开发的时候经常会遇到,比如 写了一句查询5条记录的语句 “SELECT top 5 *