Re: Join Advice and Assistance

Gary Chambers wrote:
> All,
>
> I've encountered a mental block due primarily to my inexperience with
> moderately complex joins. Given the following three tables:
>
> Table "public.users"
> Column | Type | Modifiers
> -----------+------------------------+-----------------------
> userid | bigint | not null
> lname | character varying(64) | not null
> fname | character varying(64) | not null
> passwd | character varying(64) | not null
> is_active | boolean | not null default true
>
> Table "public.user_emailaddrs"
> Column | Type | Modifiers
> -----------+------------------------+-----------------------
> userid | bigint | not null
> emailaddr | character varying(256) | not null
> is_active | boolean | not null default true
>
> Table "public.usermetas"
> Column | Type | Modifiers
> ----------------+-----------------------------+------------------------
> userid | bigint | not null
> startdate | timestamp without time zone | not null default now()
> lastlogindate | timestamp without time zone | not null default now()
> lastpwchange | timestamp without time zone | not null default now()
> logincount | integer | not null default 1
>
> users and usermetas is a one-to-one relationship.
> users and user_emailaddrs is a one-to-many relationship.
>
> What is the best way to get these tables joined on userid and return
> all emailaddr records from user_emailaddrs (e.g. if userid has three
> (3) e-mail addresses in user_emailaddrs)? Is there any way to avoid
> returning all fields in triplicate? Please feel free to criticize
> where necessary. Thank you very much in advance.
>
> -- Gary Chambers
>
> /* Nothing fancy and nothing Microsoft! */
>
>
If you want records for user without email addresses you will need an
outer join on user_emailaddrs

/* untested */
select u.userId, u.lname, u.lastname ,m.startdate, a.emailaddr
from users u
join usermetas m on u.userid = m.userid
left join user_emailaddrs a on m.userid = a.userid