Re[4]: [SQL] Query to eliminate duplicates

Hello Mario,

giovedì, 3 dicembre 98, you wrote:

MF> On 03-Dec-98 Sferacarta Software wrote:
>> Hello Mario,
>>
>> giovedì, 3 dicembre 98, you wrote:
>>
>>
>> MF> On 02-Dec-98 Sferacarta Software wrote:
>>>> MF> Is there a way to eliminate duplicate records using just SQL?
>>>>
>>>> SELECT DISTINCT ...
>>
>> MF> I deserved that!
>>
>> MF> The problem is that i have a table where there are duplicate
>> records
>> MF> and i want to delete them! I tryed creating a unique index but it told me
>> it
>> MF> couldn't because it didn't have a function to do something (I think it is
>> MF> because i had a boolean field in it)
>>
>>
>> select * from TABELA where COLUNA in (
>> select COLUNA from TABELA group by COLUNA having 1 < count(COLUNA)
>> );
>>
MF> This would work (i believe you) but in my case i'm looking into a table
MF> where there are at least 3 columns to look at!

MF> It's a table where I keep the information about wich are the
MF> disciplines where a student is enrolled:

MF> Ex:

MF> numero_aluno|codigo_disciplina|ano_lectivo|epoca|semestre
MF> ------------+-----------------+-----------+-----+--------
MF> 10335| 1207|1998/1999 | 1|f
MF> 10335| 1208|1998/1999 | 1|f
MF> 10335| 1209|1998/1999 | 1|f
MF> 10335| 1203|1998/1999 | 1|f
MF> 10335| 1205|1998/1999 | 1|f
MF> 10335| 1212|1998/1999 | 1|f
MF> 10335| 1213|1998/1999 | 1|f
MF> 10335| 1215|1998/1999 | 1|f

MF> In this case there are no duplicates but in this one there are:

MF> numero_aluno|codigo_disciplina|ano_lectivo|epoca|semestre
MF> ------------+-----------------+-----------+-----+--------
MF> 13427| 35|1998/1999 | 1|t
MF> 13427| 904|1998/1999 | 1|f
MF> 13427| 122|1998/1999 | 1|t
MF> 13427| 907|1998/1999 | 1|f
MF> 13427| 481|1998/1999 | 1|f
MF> 13427| 286|1998/1999 | 1|t
MF> 13427| 368|1998/1999 | 1|t
MF> 13427| 35|1998/1999 | 1|t
MF> 13427| 904|1998/1999 | 1|f
MF> 13427| 122|1998/1999 | 1|t

MF> So a duplicate is actually a record that looks exactly like other record on the
MF> table...

MF> Thanks for your help anyway

MF> Mario Filipe
MF> mjnf(at)uevora(dot)pt
MF> http://neptuno.sc.uevora.pt/~mjnf

select * from cursos;
numero_aluno|codigo_disciplina|ano_lectivo|epoca|semestre
------------+-----------------+-----------+-----+--------
13427| 35|1998/1999 | 1|t
13427| 904|1998/1999 | 1|f
13427| 122|1998/1999 | 1|t
13427| 907|1998/1999 | 1|f
13427| 481|1998/1999 | 1|f
13427| 286|1998/1999 | 1|t
13427| 368|1998/1999 | 1|t
13427| 35|1998/1999 | 1|t
13427| 904|1998/1999 | 1|f
13427| 122|1998/1999 | 1|t
(10 rows)

create table temp as select distinct * from cursos;
SELECT
select * from temp;
numero_aluno|codigo_disciplina|ano_lectivo|epoca|semestre
------------+-----------------+-----------+-----+--------
13427| 35|1998/1999 | 1|t
13427| 122|1998/1999 | 1|t
13427| 286|1998/1999 | 1|t
13427| 368|1998/1999 | 1|t
13427| 481|1998/1999 | 1|f
13427| 904|1998/1999 | 1|f
13427| 907|1998/1999 | 1|f
(7 rows)

DROP TABLE cursos;
DROP
alter table temp rename to cursos;
RENAME

-Jose'-