在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢
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 peopleName in (select peopleName from people group by peopleName having count(peopleName) > 1)
and peopleId not in (select min(peopleId) from people group by peopleName having count(peopleName)>1)
3、查找表中多余的重复记录（多个字段）
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
delete from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
6.消除一个字段的左边的第一位：
update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like '村%'
7.消除一个字段的右边的第一位：
update tableName set [Title]=left([Title],(len([Title])-1)) where Title like '%村'
8.假删除表中多余的重复记录（多个字段），不包含rowid最小的记录
update vitae set ispass=-1
where peopleId in (select peopleId from vitae group by peopleId
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删除重复数据只保存一条--ms sql及oracle实现方法 ms sql方法： declare @sss table (ID int, Name varchar(10), address varchar(10)) insert into @sss select 1,'小王','重庆' insert into @sss select 2,'小张','北京' insert into @sss select 3,'小明','上海' insert into @sss select 4,'小红','重庆' insert into @sss select 5,'小李','重庆' insert into @sss select 6,'小白','北京' insert into @sss select 7,'小红','上海' insert into @sss select 8,'小红','重庆' delete from @sss where id not in(select min(id) from @sss group by name,address) ------------------------------------------------------------------------------------------------------------ oracle方法： SQL> CREATE TABLE test_delete( 2 name varchar(10), 3 value INT 4 ); 表已创建。 SQL> INSERT INTO test_delete 2 SELECT '张三', 100 FROM dual 3 UNION ALL SELECT '张三', 100 FROM dual 4 UNION ALL SELECT '李四', 80 FROM dual 5 UNION ALL SELECT '王五', 80 FROM dual 6 UNION ALL SELECT '王五', 80 FROM dual 7 UNION ALL SELECT '赵六', 90 FROM dual 8 UNION ALL SELECT '赵六', 70 FROM dual; 已创建7行。 SQL> SELECT 2 ROWID, 3 name, 4 value 5 FROM 6 test_delete; ROWID NAME VALUE ------------------ ---------- ---------- AAAM2mAAGAAAAOXAAA 张三 100 AAAM2mAAGAAAAOXAAB 张三 100 AAAM2mAAGAAAAOXAAC 李四 80 AAAM2mAAGAAAAOXAAD 王五 80 AAAM2mAAGAAAAOXAAE 王五 80 AAAM2mAAGAAAAOXAAF 赵六 90 AAAM2mAAGAAAAOXAAG 赵六 70 已选择7行。
SQL> DELETE 2 test_delete 3 WHERE 4 (name, value) 5 IN (SELECT 6 name, value 7 FROM 8 test_delete 9 GROUP BY 10 name, value 11 HAVING COUNT(1) > 1) 12 AND rowid NOT IN 13 (SELECT 14 MIN(rowid) 15 FROM 16 test_delete 17 GROUP BY 18 name, value 19 HAVING 20 COUNT(1) > 1); 已删除2行。 SQL> SELECT 2 ROWID, 3 name, 4 value 5 FROM 6 test_delete; ROWID NAME VALUE ------------------ ---------- ---------- AAAM2mAAGAAAAOXAAA 张三 100 AAAM2mAAGAAAAOXAAC 李四 80 AAAM2mAAGAAAAOXAAD 王五 80 AAAM2mAAGAAAAOXAAF 赵六 90 AAAM2mAAGAAAAOXAAG 赵六 70