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@uevora.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'-