Select from 4 tables but include data from 3 even if 4th is null

Question

Hello -
I'm quite new to oracle and apex, but enjoying learning - but sometimes I need a gentle nudge to know what I need to learn about.
I have a select statement that works - selecting specific columns from 3 tables:
SELECT
"TERRITORIES"."TER_NAME" "TER_NAME",
"TERRITORY_TYPES"."TTP_DESCRIPTION" "TTP_DESCRIPTION",
"COUNTRIES"."CNT_DESCRIPTION" "COUNTRY"
FROM
"TERRITORIES", "TERRITORY_TYPES","COUNTRIES"
WHERE
"TERRITORIES"."TER_TTP_ID"="TERRITORY_TYPES"."TTP_ID"
and
"COUNTRIES"."CNT_TER_ID"="TERRITORIES"."TER_ID"
I want to add in a 4th table for, you guessed it, States.
However, many of the countries do not yet have states in the states table (and may never have any). Therefore, they do not appear in the results. I want them included in the query, so that I'll have the opportunity to add in the data via Apex.
Is there a phrase I can insert in the 1st query so that I'll get data for Territory Type, Territory and Country, even if the State table is null?
Or, do I need to insert records into the state table, such as: insert into states (state_ID, STATE_CNT_ID) values (state_seq.nextval,2). If so, do I just do that over and over, replacing the value? Or is this where I need to learn about bind variables? Or some other command?
Thank you-
Marion in NY
Edited by: mtpaper on Oct 24, 2009 12:54 PM
I FIGURED IT OUT! I DID IT! How do I mark myself as helpful???
insert INTO states
(state_ID, STATE_CNT_ID)
SELECT state_seq.nextval, cnt_id
FROM countries
WHERE not exists (select * from states where states.state_cnt_id = countries.cnt_id)
Edited by: mtpaper on Oct 24, 2009 1:10 PM

Answer 1

You certainly could insert data into the STATES table, but I generally wouldn't advise inserting rows into a STATES table for states that don't actually exist. It would seem to make far more sense to just do an outer join when you include the STATES table in your query
SELECT "TERRITORIES"."TER_NAME" "TER_NAME",
       "TERRITORY_TYPES"."TTP_DESCRIPTION" "TTP_DESCRIPTION",
       "COUNTRIES"."CNT_DESCRIPTION" "COUNTRY",
       s.state_name
  FROM TERRITORIES t ,
       TERRITORY_TYPES tt,
       COUNTRIES c,
       states s
WHERE "TERRITORIES"."TER_TTP_ID"="TERRITORY_TYPES"."TTP_ID"
   and "COUNTRIES"."CNT_TER_ID"="TERRITORIES"."TER_ID"
   and c.cnt_id = s.state_cnt_id(+)The {noformat}(+){noformat} operator indicates that you want to do an outer join. So if there is no row in the STATES table that matches the join condition, a NULL is returned.
From a purely stylistic standpoint, I would generally suggest using aliases (i.e. the T, TT, C, and S in the FROM clause) rather than having to constantly write out all the table names. And I wouldn't suggest putting double-quotes around everything-- that forces all your identifiers to be upper case and case sensitive.
Justin