RE: ambiguous

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От Tamsin
Тема RE: ambiguous
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Msg-id NEBBKHBOBMJCHDMGKCNJOEMDCKAA.tg_mail@bryncadfan.co.uk
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Ответ на ambiguous  (si <s@remail.net>)
Список pgsql-novice
You need to qualify which dept_id you are refering to in your where clause:

select * from department, employee where department.dept_no = '1';

Also, unless you join the two tables in your where clause you'll get a
cartesian join, so you might want to do:

select * from department, employee
where department.dept_no = '1' and department.dept_no = employee.dept_no;

You can also use aliases for your tablenames to save typing:

select * from department d, employee e
where d.dept_no = '1' and d.dept_no = e.dept_no;

Hope this helps,
Tamsin


> -----Original Message-----
> From: pgsql-novice-owner@postgresql.org
> [mailto:pgsql-novice-owner@postgresql.org]On Behalf Of si
> Sent: 07 March 2001 15:33
> To: pgsql-novice@postgresql.org
> Subject: [NOVICE] ambiguous
>
>
> If I assign the same name to 2 columns in 2 different tables:
>
> +--------------------------------------+
> |              DEPARTMENT              |
> +----------+----------------+----------+
> | LOCATION |  DESCRIPTION   |  DEPT_NO |
> +----------+----------------+----------+
> | Bedrock  | Administration |     1    |
> +----------+----------------+----------+
>
> +--------------------------------+
> |            EMPLOYEE            |
> +---------+------------+---------+
> | EMPL_ID | NAME_LAST  | DEPT_NO |
> +---------+------------+---------+
> |    1    | Slate      |     1   |
> +---------+------------+---------+
>
> select * from DEPARTMENT, Employee where dept_no = '1';
>
> PG throws up:
> ERROR:  Column 'dept_no' is ambiguous
>
> Is this not allowed? or is my sql understanding wrong?
>
>
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