SQL LEFT JOIN combined with regular joins - sql

Question

I have the following query that joins a bunch of tables.
I'd like to get every record from the INDUSTRY table that has consolidated_industry_id = 1 regardless of whether or not it matches the other tables. I believe this needs to be done with a LEFT JOIN?
SELECT attr.industry_id AS option_id,
attr.industry AS option_name,
uj.ft_job_industry_id,
Avg(CASE
WHEN s.salary > 0 THEN s.salary
END) AS average,
Count(CASE
WHEN s.salary > 0 THEN attr.industry
END) AS count_non_zero,
Count(attr.industry_id) AS count_total
FROM industry attr,
user_job_ft_job uj,
salary_ft_job s,
user_job_ft_job ut,
[user] u,
user_education_mba_school mba
WHERE u.user_id = uj.user_id
AND u.user_id = ut.user_id
AND u.user_id = mba.user_id
AND uj.ft_job_industry_id = attr.industry_id
AND uj.user_job_ft_job_id = s.user_job_id
AND u.include_in_student_site_results = 1
AND u.site_instance_id IN ( 1 )
AND uj.job_type_id = 1
AND attr.consolidated_industry_id = 1
AND mba.mba_graduation_year_id NOT IN ( 8, 9 )
AND uj.admin_approved = 1
GROUP BY attr.industry_id,
attr.industry,
uj.ft_job_industry_id
This returns only one row, but there are 8 matches in the industry table where consolidated_industry_id = 1.
--- EDIT: The real question here is, how do I combine the LEFT JOIN with the regular joins?

Answer 1

Use left join for tables that may miss a corresponding record. Put the conditions for each table in the on clause of the join, not in the where, as that would in effect make them inner joins anyway. Something like:
select
attr.industry_id AS option_id, attr.industry AS option_name,
uj.ft_job_industry_id, AVG(CASE WHEN s.salary > 0 THEN s.salary END) AS average,
COUNT(CASE WHEN s.salary > 0 THEN attr.industry END) as count_non_zero,
COUNT(attr.industry_id) as count_total
from
industry attr
left join user_job_ft_job uj on uj.ft_job_industry_id = attr.industry_id and uj.job_type_id = 1 and uj.admin_approved = 1
left join salary_ft_job s on uj.user_job_ft_job_id = s.user_job_id
left join [user] u on u.user_id = uj.user_id and u.include_in_student_site_results = 1 and u.site_instance_id IN (1)
left join user_job_ft_job ut on u.user_id = ut.user_id
left join user_education_mba_school mba on u.user_id = mba.user_id and mba.mba_graduation_year_id not in (8, 9)
where
attr.consolidated_industry_id = 1
group by
attr.industry_id, attr.industry, uj.ft_job_industry_id
If you have any tables that you know always have a corresponding record, just use innser join for that.