Обсуждение: query assistance

Is there a straight forward way to pull out duplicates in a particular field given a value in another field?
For example, I have a table that lists users and study names associated with those users. Each user can have one or more study names. My goal is to determine if any of these people have duplicate study names. There are duplicated study names across the system and that is ok. I just want to see if any users have duplicate study names among their studies.
My table looks like this:

                                   Table "public.study"
    Column    |            Type             |                Modifiers                
--------------+-----------------------------+------------------------------------------
 sty_pk       | integer                     | not null default nextval('pk_seq'::text)
 study_name   | character varying(128)      | not null
 start_date   | timestamp without time zone |
 sty_comments | text                        |
 created_by   | integer                     |
Indexes: study_pkey primary key btree (sty_pk)

I am concerened with study_name. The created_by field tells me who owns it.
Thanks
Jodi

On Tuesday 04 November 2003 15:16, Jodi Kanter wrote:
> Is there a straight forward way to pull out duplicates in a particular
> field given a value in another field?
> For example, I have a table that lists users and study names associated
> with those users. Each user can have one or more study names. My goal is
> to determine if any of these people have duplicate study names. There
> are duplicated study names across the system and that is ok. I just want
> to see if any users have duplicate study names among their studies.

Something like:

SELECT created_by, study_name, count(sty_pk)
FROM study
GROUP BY created_by, study_name
HAVING count(sty_pk) > 1;

--  Richard Huxton Archonet Ltd

Hi Jodi,

On Wednesday, November 5, 2003, at 12:16 AM, Jodi Kanter wrote:

> Is there a straight forward way to pull out duplicates in a particular=20=
=20
> field given a value in another field?
> For example, I have a table that lists users and study names=20=20
> associated with those users. Each user can have one or more study=20=20
> names.

If I understand you correctly, this is the table you're interested in.=20=
=20
Your public.study table doesn't include any users as far as I can tell=20=
=20
(though please correct me if I'm misunderstanding you).

> =A0=A0=A0 =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0 Table "public.study"
> =A0=A0=A0 Column=A0=A0=A0 |=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 Type=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 |=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=20=20
> Modifiers=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0
> --------------+-----------------------------=20
> +------------------------------------------
> =A0sty_pk=A0=A0=A0=A0=A0=A0 | integer=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0 | not null default=20=20
> nextval('pk_seq'::text)
> =A0study_name=A0=A0 | character varying(128)=A0=A0=A0=A0=A0 | not null
> =A0start_date=A0=A0 | timestamp without time zone |
> =A0sty_comments | text=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0 |
> =A0created_by=A0=A0 | integer=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0 |
> Indexes: study_pkey primary key btree (sty_pk)

I think something like this is what you're looking for:

SELECT user, study_name, COUNT(*)
FROM <table linking user and study_name>
GROUP BY user, study_name
HAVING COUNT(*) > 1;

where the FROM clause lists the table linking users and study_names.

Does this help?

Michael
grzm myrealbox com