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help required to wrire a query.

Roy4321
Roy4321 Member Posts: 305 Bronze Badge
edited Dec 8, 2009 6:15AM in SQL & PL/SQL
Hi,
I have the below data

TableA

name----id----status
mat----123---- 1
mat----123---- 2 -- to be deleted
mat----123---- 2 -- to be deleted
sam----456---- 2
sam----456---- 2 -- to be deleted
dan----789---- 1
dan----789---- 1 -- to be deleted
dan----789---- 2 -- to be deleted
pan----111---- 1


can someone give me an idea how to write a query that delletes the records marked as "-- to be deleted"

Thanks,
Mathew

Edited by: [email protected] on Dec 4, 2009 12:21 AM
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Answers

  • MaheshKaila
    MaheshKaila Member Posts: 310 
    DELETE FROM table_name t1
WHERE (EXISTS
          (SELECT ROWID
           FROM table_name t2
           WHERE t1.name = t2.name
                 AND t1.id = t2.id
                 AND t1.status = t2.status
                 AND t2.ROWID > t1.ROWID))
                 
                 
DELETE FROM table_name t1
WHERE (EXISTS
          (SELECT ROWID
           FROM table_name t2
           WHERE t1.name = t2.name
                 AND t1.id = t2.id
                 AND t1.status <> '1'
                 AND t2.ROWID > t1.ROWID))
    Regards,
    Mahesh Kaila
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  • 21205
    21205 Member Posts: 6,168 Gold Trophy
    What is the logic behind this? Why are those records identified as to be deleted?
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  • 523888
    523888 Member Posts: 208
    I think this might work
    delete from t where rowid not in 
(select min(rowid) from t 
group by name,id)
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  • Roy4321
    Roy4321 Member Posts: 305 Bronze Badge
    Those are actually duplicate records ...only it differs in status...but if there is a record with status as 1 i want to keep that record and delete the rest..but if records are only present with status 2 then the first record with status 2 needs to be deleted --these are for each ID.

    hope this helps!!
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  • Roy4321
    Roy4321 Member Posts: 305 Bronze Badge
    this will not work...as i will need to keep the record with status as 1 if it exists.
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  • 21205
    21205 Member Posts: 6,168 Gold Trophy
    something like? 
    SQL> create table test
  2  as
  3  select 'mat' name, 123 id, 1 status from dual union all
  4  select 'mat' name, 123 id, 2 status from dual union all -- to be deleted
  5  select 'mat' name, 123 id, 2 status from dual union all -- to be deleted
  6  select 'sam' name, 456 id, 2 status from dual union all
  7  select 'sam' name, 456 id, 2 status from dual union all -- to be deleted
  8  select 'dan' name, 789 id, 1 status from dual union all
  9  select 'dan' name, 789 id, 1 status from dual union all -- to be deleted
 10  select 'dan' name, 789 id, 2 status from dual union all -- to be deleted
 11  select 'pan' name, 111 id, 1 status from dual
 12  /

Table created.

SQL> 
SQL> delete from test
  2   where rowid in 
  3     (select rid
  4        from (
  5           select rowid rid
  6                , row_number() over (partition by name, id
  7                                         order by status
  8                                    ) rn
  9             from test
 10        )
 11       where rn > 1
 12     )
 13  /

5 rows deleted.

SQL> 
SQL> select *
  2    from test
  3  /

NAM         ID     STATUS
--- ---------- ----------
mat        123          1
sam        456          2
dan        789          1
pan        111          1

SQL> 
SQL> drop table test purge
  2  /

Table dropped.

SQL>
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  • 523888
    523888 Member Posts: 208
    then what about this row that you mentioned 

    sam----456---- 2
sam----456---- 2 -- to be deleted
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  • Roy4321
    Roy4321 Member Posts: 305 Bronze Badge
    Thanks Alex...that works!!
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  • Roy4321
    Roy4321 Member Posts: 305 Bronze Badge
    if i am correct the query you wrote will take the min rowid and delete the rest..but if min(rowid) is not for status 1 then this gets deleted too...
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  • 523888
    523888 Member Posts: 208 
    create table test2
as
(select 'mat' name, 123 id, 1 status from dual union all
select 'mat' name, 123 id, 2 status from dual union all -- to be deleted
select 'mat' name, 123 id, 2 status from dual union all -- to be deleted
select 'sam' name, 456 id, 2 status from dual union all
select 'sam' name, 456 id, 2 status from dual union all -- to be deleted
select 'dan' name, 789 id, 1 status from dual union all
select 'dan' name, 789 id, 1 status from dual union all -- to be deleted
select 'dan' name, 789 id, 2 status from dual union all -- to be deleted
select 'pan' name, 111 id, 1 status from dual
);

select * from test2;

NAME	ID	STATUS
mat	123	1
mat	123	2
mat	123	2
sam	456	2
sam	456	2
dan	789	1
dan	789	1
dan	789	2
pan	111	1

delete from test2 where rowid not in 
(select min(rowid) from test2
group by name,id);

5 rows deleted

select * from test2;

NAME	ID	STATUS
mat	123	1
sam	456	2
dan	789	1
pan	111	1
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