Обсуждение: Select / sub select? query... help...
Hello -
I'm trying to figure out how to write a particular query and need some
assistance. I imagine this is extremely simple. I have the table defined
below with five records. This table keeps track of peoples names. Each
person has a unique ID number ("person_id"). The table can also keep track
of alias names for these people. Each record has a flag ("isalias")
indicating whether or not this record indicates a persons real name or a
persons alias name. If it is an alias name then an additional field
("alias") has the number indicating this persons real name record by
person_id (ie alias field of an alias record == the person_id of the real
name record).
I want a query that will select all entries where "isalias" is true and
will display the person_id, first, and last fields from the alias record and
ALSO the first and last fields from the real name entry.
Output would be something like this for the example data below
3 - Johns - Alias - John - Smith
4 - Marks - Alias - Mark - Twain
Any thoughts on how this can be accomplished easily / efficiently?
Thanks
-Jim
Table "public.people"
Column | Type | Modifiers
-----------+-----------------------+-----------
person_id | integer |
first | character varying(20) |
last | character varying(20) |
alias | integer |
isalias | boolean |
Containing the example data:
person_id | first | last | alias | isalias
-----------+-------+-------+-------+---------
1 | John | Smith | 0 | f
2 | Mark | Twain | 0 | f
3 | Johns | Alias | 1 | t
4 | Marks| Alias | 2 | t
5 | someone | else | 0| f
(5 rows)
Not sure if I have this the right way round, but one option is a self-join
select p2.first, p2.last, p1.first, p1.last
from people p1, people p2
where p1.person_id = p2.alias
and p2.isalias = true;
Another is to use a sub-select as a column result (haven't checked the
SQL for mistakes)
select p2.first, p2.last, (select first||' - '||last from person p1
where p2.alias = p1.person_id) as realname
from person p2
and p2.isalias = true;
Hope that helps as a starting point.
John
Jim Fitzgerald wrote:
> Hello -
>
> I'm trying to figure out how to write a particular query and need some
> assistance. I imagine this is extremely simple. I have the table defined
> below with five records. This table keeps track of peoples names. Each
> person has a unique ID number ("person_id"). The table can also keep track
> of alias names for these people. Each record has a flag ("isalias")
> indicating whether or not this record indicates a persons real name or a
> persons alias name. If it is an alias name then an additional field
> ("alias") has the number indicating this persons real name record by
> person_id (ie alias field of an alias record == the person_id of the real
> name record).
>
> I want a query that will select all entries where "isalias" is true and
> will display the person_id, first, and last fields from the alias record and
> ALSO the first and last fields from the real name entry.
>
> Output would be something like this for the example data below
>
> 3 - Johns - Alias - John - Smith
> 4 - Marks - Alias - Mark - Twain
>
>
> Any thoughts on how this can be accomplished easily / efficiently?
>
> Thanks
> -Jim
>
>
> Table "public.people"
> Column | Type | Modifiers
> -----------+-----------------------+-----------
> person_id | integer |
> first | character varying(20) |
> last | character varying(20) |
> alias | integer |
> isalias | boolean |
>
> Containing the example data:
>
> person_id | first | last | alias | isalias
> -----------+-------+-------+-------+---------
> 1 | John | Smith | 0 | f
> 2 | Mark | Twain | 0 | f
> 3 | Johns | Alias | 1 | t
> 4 | Marks| Alias | 2 | t
> 5 | someone | else | 0| f
>
> (5 rows)
>
>
>
>
> ---------------------------(end of broadcast)---------------------------
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Jim Fitzgerald wrote:
>Hello -
>
>
Probably would be better to ask, "how do I store this data?"
Then the query writes itself. Put people in one table, put aliases in
another.
CREATE TABLE people (
person_id int
,first varchar(20)
,last varchar(20)
)
CREATE TABLE aliases (
person_id int references people (person_id)
,first varchar(20)
,last varchar(20)
)
> I'm trying to figure out how to write a particular query and need some
>assistance. I imagine this is extremely simple. I have the table defined
>below with five records. This table keeps track of peoples names. Each
>person has a unique ID number ("person_id"). The table can also keep track
>of alias names for these people. Each record has a flag ("isalias")
>indicating whether or not this record indicates a persons real name or a
>persons alias name. If it is an alias name then an additional field
>("alias") has the number indicating this persons real name record by
>person_id (ie alias field of an alias record == the person_id of the real
>name record).
>
> I want a query that will select all entries where "isalias" is true and
>will display the person_id, first, and last fields from the alias record and
>ALSO the first and last fields from the real name entry.
>
>Output would be something like this for the example data below
>
>3 - Johns - Alias - John - Smith
>4 - Marks - Alias - Mark - Twain
>
>
>Any thoughts on how this can be accomplished easily / efficiently?
>
>Thanks
>-Jim
>
>
> Table "public.people"
> Column | Type | Modifiers
>-----------+-----------------------+-----------
> person_id | integer |
> first | character varying(20) |
> last | character varying(20) |
> alias | integer |
> isalias | boolean |
>
>Containing the example data:
>
> person_id | first | last | alias | isalias
>-----------+-------+-------+-------+---------
> 1 | John | Smith | 0 | f
> 2 | Mark | Twain | 0 | f
> 3 | Johns | Alias | 1 | t
> 4 | Marks| Alias | 2 | t
> 5 | someone | else | 0| f
>
>(5 rows)
>
>
>
>
>---------------------------(end of broadcast)---------------------------
>TIP 1: if posting/reading through Usenet, please send an appropriate
> subscribe-nomail command to majordomo@postgresql.org so that your
> message can get through to the mailing list cleanly
>
>
Вложения
Thanks for the advice.. I got it working!
-Jim
"Jim Fitzgerald" <jfitz@spacelink.com> wrote in message
news:e30gad$i7$1@news.hub.org...
> Hello -
>
> I'm trying to figure out how to write a particular query and need some
> assistance. I imagine this is extremely simple. I have the table defined
> below with five records. This table keeps track of peoples names. Each
> person has a unique ID number ("person_id"). The table can also keep
> track of alias names for these people. Each record has a flag ("isalias")
> indicating whether or not this record indicates a persons real name or a
> persons alias name. If it is an alias name then an additional field
> ("alias") has the number indicating this persons real name record by
> person_id (ie alias field of an alias record == the person_id of the real
> name record).
>
> I want a query that will select all entries where "isalias" is true and
> will display the person_id, first, and last fields from the alias record
> and ALSO the first and last fields from the real name entry.
>
> Output would be something like this for the example data below
>
> 3 - Johns - Alias - John - Smith
> 4 - Marks - Alias - Mark - Twain
>
>
> Any thoughts on how this can be accomplished easily / efficiently?
>
> Thanks
> -Jim
>
>
> Table "public.people"
> Column | Type | Modifiers
> -----------+-----------------------+-----------
> person_id | integer |
> first | character varying(20) |
> last | character varying(20) |
> alias | integer |
> isalias | boolean |
>
> Containing the example data:
>
> person_id | first | last | alias | isalias
> -----------+-------+-------+-------+---------
> 1 | John | Smith | 0 | f
> 2 | Mark | Twain | 0 | f
> 3 | Johns | Alias | 1 | t
> 4 | Marks| Alias | 2 | t
> 5 | someone | else | 0| f
>
> (5 rows)
>
>
>