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orAClE某个字段有重复数据,如何删除多余数据只保...

oracle中在一张表中某个字段下面有重复记录,有很多方法,但是有一个方法,是比较"高效"的,如下语句: SELECT data_guid FROM adam_entity_datas a WHERE a.rowid > (SELECT MIN(b.rowid) FROM adam_entity_datas b WHERE b.data_guid = a.data...

查询及删除重复记录的SQL语句 1、查找表中多余的重复记录,重复记录是根据单个字段(Id)来判断 ; select * from 表 where Id in (select Id from 表 group byId having count(Id) > 1) 2、删除表中多余的重复记录,重复记录是根据单个字段(Id...

select * from A, (select max(id) id_m, 某个字段 from A group by 某个字段) B where A.id = B.id_m

SELECT * FROM 表名 main WHERE NOT EXISTS ( SELECT 1 FROM 表名 sub WHERE main.姓名 = sub.姓名 AND main.年龄 < sub.年龄 ) 算法是, 对于每一个 姓名, 仅仅检索出 年龄最大的那行数据. ( 这个 SQL 的缺点在于: 如果你有2行, 姓名一样, 年...

oracle中查询及删除重复记录的SQL语句: 1、查找表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断 SELECT * FROM people WHERE peopleid IN (SELECT peopleid FROM people GROUP BY peopleid HAVING COUNT(peopleid) > 1) 2、删除...

select * from A, (select max(id) id_m, 某个字段 from A group by 某个字段) B where A.id = B.id_m

取某一字段不重复记录可用distinct或者group by来实现。 如,emp表中有如下数据: 要求取出deptno字段所有的不重复记录,可分别用以下两个语句: 1、 select distinct deptno from emp;2、 select deptno from emp group by deptno;结果如下:

CREATE TABLE #test ( ID int, name varchar(10), age int);go-- 用于测试 楼主的原始数据.INSERT INTO #testSELECT 1, 'tom', 22 UNION ALLSELECT 2, 'tom', 23 UNION ALLSELECT 3, 'tom', 24 UNION ALLSELECT 4, 'lily', 22 UNION ALLSELECT 5...

SELECT DISTINCT CAR_NO FROM BGTY_EXE_BGZXCARA WHERE RPT_TIME BETWEEN '2017-06-01 00:00:00' AND '2017-06-30 23:59:59' AND (CAR_NO IS NOT NULL OR CAR_NO != '' OR CAR_NO != ' ') AND WB_YDQX != '0'

实际上题目考察的就是分组求和。可以通过sum进行求和,count进行数值计算,通过group by进行分组。 sql:select username ,count(accountNo) as count,sum(amount) as amount from tablename group by username; 以上就可以求出username下,acco...

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