Обсуждение: SELECT help (fwd)

I am trying to do a select similar to the one below:

SELECT individual.first, individual.last, title_value.title
FROM individual, title_value, individual_staff_join_unit
WHERE individual.individual_id = 5307809
      AND
      individual_staff_join_unit.main_id = individual.main_id
      AND
      title_value.title_id = individual_staff_join_unit.title_id;

                  Table "individual"
 Attribute        |          Type          | Modifier
------------------+------------------------+----------
 individual_id    | integer                |
 main_id          | integer                |
 first            | character varying(40)  |
 last             | character varying(40)  |

    Table "individual_staff_join_unit"
 Attribute   |  Type   | Modifier
-------------+---------+----------
 main_id     | integer |
 unit_id     | integer |
 title_id    | integer |

               Table "title_value"
 Attribute |         Type          | Modifier
-----------+-----------------------+----------
 title_id  | integer               |
 title     | character varying(40) |

Every individual has a individual_id and a main_id.

The problem is that some rows in the individual_staff_join_unit table have
title_id = 0 and there is no row in title_value with title = 0. If this is
the case then no row is retrieved for the above SELECT.

Q: Is it possible to still get the individual.first and individual.last
from the table if the individual_staff_join_unit.title_id = 0 using only
one select statement and without modifying any of the tables, and to get
individual.first, individual.last and title_value.title if
individual_staff_join_unit.title_id != 0?

--
David A Dickson
david.dickson@mail.mcgill.ca

You could use a LEFT OUTER JOIN on the table with the title = 0

This would return NULLS for that field if it did not exist in the table
but would still return rows

And if the NULL was a problem then you could use the COALESCE function
to change the NULL value to whatever you wanted.

Would look something like this

SELECT individual.first,individual.last,title_value.title
FROM individual
     LEFT OUTER JOIN individual_staff_join_unit ON
          individual_staff_join_unit.main_id = individual.main_id,
     title_value
WHERE individual.individual_id = 5307809 AND
      individual_staff_join_unit.main_id = individual.main_id AND
      title_value.title_id = individual_staff_join_unit.title_id;

I think i understood but looking back maybe not. If this is not write then
i misunderstood

But i think it should be fine

Darren Ferguson

On Mon, 14 Jan 2002, David A Dickson wrote:

> I am trying to do a select similar to the one below:
>
> SELECT individual.first, individual.last, title_value.title
> FROM individual, title_value, individual_staff_join_unit
> WHERE individual.individual_id = 5307809
>       AND
>       individual_staff_join_unit.main_id = individual.main_id
>       AND
>       title_value.title_id = individual_staff_join_unit.title_id;
>
>                   Table "individual"
>  Attribute        |          Type          | Modifier
> ------------------+------------------------+----------
>  individual_id    | integer                |
>  main_id          | integer                |
>  first            | character varying(40)  |
>  last             | character varying(40)  |
>
>     Table "individual_staff_join_unit"
>  Attribute   |  Type   | Modifier
> -------------+---------+----------
>  main_id     | integer |
>  unit_id     | integer |
>  title_id    | integer |
>
>                Table "title_value"
>  Attribute |         Type          | Modifier
> -----------+-----------------------+----------
>  title_id  | integer               |
>  title     | character varying(40) |
>
> Every individual has a individual_id and a main_id.
>
> The problem is that some rows in the individual_staff_join_unit table have
> title_id = 0 and there is no row in title_value with title = 0. If this is
> the case then no row is retrieved for the above SELECT.
>
> Q: Is it possible to still get the individual.first and individual.last
> from the table if the individual_staff_join_unit.title_id = 0 using only
> one select statement and without modifying any of the tables, and to get
> individual.first, individual.last and title_value.title if
> individual_staff_join_unit.title_id != 0?
>
> --
> David A Dickson
> david.dickson@mail.mcgill.ca
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
>
> http://www.postgresql.org/users-lounge/docs/faq.html
>

Thanks for the help Darren but that didn't work. It did set me on the
right track however and I came up with the following solution:

SELECT     individual.first, individual.last, title_value.title
FROM     individual_staff_join_unit
    LEFT OUTER JOIN title_value
    ON individual_satff_join_unit.title_id = title_value.ttle_id,
    individual
WHERE    individual.individual_id = 5307809
    AND individual_staff_join_unit.main_id = individual.main_id;

On Mon, 14 Jan 2002, Darren Ferguson wrote:

> You could use a LEFT OUTER JOIN on the table with the title = 0
>
> This would return NULLS for that field if it did not exist in the table
> but would still return rows
>
> And if the NULL was a problem then you could use the COALESCE function
> to change the NULL value to whatever you wanted.
>
> Would look something like this
>
> SELECT individual.first,individual.last,title_value.title
> FROM individual
>      LEFT OUTER JOIN individual_staff_join_unit ON
>           individual_staff_join_unit.main_id = individual.main_id,
>      title_value
> WHERE individual.individual_id = 5307809 AND
>       individual_staff_join_unit.main_id = individual.main_id AND
>       title_value.title_id = individual_staff_join_unit.title_id;
>
> I think i understood but looking back maybe not. If this is not write then
> i misunderstood
>
> But i think it should be fine
>
> On Mon, 14 Jan 2002, David A Dickson wrote:
>
> > I am trying to do a select similar to the one below:
> >
> > SELECT individual.first, individual.last, title_value.title
> > FROM individual, title_value, individual_staff_join_unit
> > WHERE individual.individual_id = 5307809
> >       AND
> >       individual_staff_join_unit.main_id = individual.main_id
> >       AND
> >       title_value.title_id = individual_staff_join_unit.title_id;
> >
> >                   Table "individual"
> >  Attribute        |          Type          | Modifier
> > ------------------+------------------------+----------
> >  individual_id    | integer                |
> >  main_id          | integer                |
> >  first            | character varying(40)  |
> >  last             | character varying(40)  |
> >
> >     Table "individual_staff_join_unit"
> >  Attribute   |  Type   | Modifier
> > -------------+---------+----------
> >  main_id     | integer |
> >  unit_id     | integer |
> >  title_id    | integer |
> >
> >                Table "title_value"
> >  Attribute |         Type          | Modifier
> > -----------+-----------------------+----------
> >  title_id  | integer               |
> >  title     | character varying(40) |
> >
> > Every individual has a individual_id and a main_id.
> >
> > The problem is that some rows in the individual_staff_join_unit table have
> > title_id = 0 and there is no row in title_value with title = 0. If this is
> > the case then no row is retrieved for the above SELECT.
> >
> > Q: Is it possible to still get the individual.first and individual.last
> > from the table if the individual_staff_join_unit.title_id = 0 using only
> > one select statement and without modifying any of the tables, and to get
> > individual.first, individual.last and title_value.title if
> > individual_staff_join_unit.title_id != 0?

--
David A Dickson
david.dickson@mail.mcgill.ca

David,

I think you will need to use an outer join to get the title=0 records look
at:

http://www.postgresql.org/idocs/index.php?queries.html#QUERIES-FROM

specifically the information relating to Left Outer Join.

hih

steve boyle

----- Original Message -----
From: "David A Dickson" <davidd@saraswati.wcg.mcgill.ca>
To: <pgsql-general@postgresql.org>
Sent: Monday, January 14, 2002 6:17 PM
Subject: [GENERAL] SELECT help (fwd)


> I am trying to do a select similar to the one below:
>
> SELECT individual.first, individual.last, title_value.title
> FROM individual, title_value, individual_staff_join_unit
> WHERE individual.individual_id = 5307809
>       AND
>       individual_staff_join_unit.main_id = individual.main_id
>       AND
>       title_value.title_id = individual_staff_join_unit.title_id;
>
>                   Table "individual"
>  Attribute        |          Type          | Modifier
> ------------------+------------------------+----------
>  individual_id    | integer                |
>  main_id          | integer                |
>  first            | character varying(40)  |
>  last             | character varying(40)  |
>
>     Table "individual_staff_join_unit"
>  Attribute   |  Type   | Modifier
> -------------+---------+----------
>  main_id     | integer |
>  unit_id     | integer |
>  title_id    | integer |
>
>                Table "title_value"
>  Attribute |         Type          | Modifier
> -----------+-----------------------+----------
>  title_id  | integer               |
>  title     | character varying(40) |
>
> Every individual has a individual_id and a main_id.
>
> The problem is that some rows in the individual_staff_join_unit table have
> title_id = 0 and there is no row in title_value with title = 0. If this is
> the case then no row is retrieved for the above SELECT.
>
> Q: Is it possible to still get the individual.first and individual.last
> from the table if the individual_staff_join_unit.title_id = 0 using only
> one select statement and without modifying any of the tables, and to get
> individual.first, individual.last and title_value.title if
> individual_staff_join_unit.title_id != 0?
>
> --
> David A Dickson
> david.dickson@mail.mcgill.ca
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
>
> http://www.postgresql.org/users-lounge/docs/faq.html
>