Converting three-table FULL OUTER JOIN query to MySQL - mysql

Question

I need to translate this query which works in SQL Server to MySQL. I've circled around it at least 50 times and am stumped and cannot even find a starting point.
The issues in a nutshell:
It has not one but two FULL OUTER joins which MySQL does not do. I
know this can be emulated some how using UNION in combination with LEFT and RIGHT joins.
It joins the tables on multiple conditions and I am not sure how to add exclusion
criteria in the ON if doing a typical RIGHT JOIN
SELECT COALESCE(ca.reporting_period, s_p.reporting_period, s_uy.reporting_period) AS reporting_period,
COALESCE(ca.state, s_p.state, s_uy.state) AS state,
COALESCE(ca.servicer, s_p.servicer, s_uy.servicer) AS servicer,
COALESCE(ca.product, s_p.product, s_uy.product) AS product,
COALESCE(ca.product_group, s_p.product_group, s_uy.product_group) AS product_group,
COALESCE(ca.portfolio, s_p.portfolio, s_uy.portfolio) AS portfolio,
COALESCE(ca.channel, s_p.channel, s_uy.channel) AS channel,
ca.Gross,
ca.Costs,
ca.commission,
ca.commissionable,
s_p.WAVG_placed_numerator,
s_p.place_balance AS WAVG_placed_denominator,
SUM(s_uy.cum_gross) AS gross_uy_num,
SUM(s_uy.cum_netnet) AS netnet_uy_num,
SUM(s_uy.cum_commission) AS servicer_uy_num,
SUM(s_uy.num_accounts) AS uy_den,
ca.costs_recovered
# INTO adhoc_work.RevenueReport_Legal
FROM adhoc_work.Cash ca
FULL OUTER JOIN adhoc_work.Summary_placed s_p
ON ca.reporting_period = s_p.reporting_period
AND ca.state = s_p.state
AND ca.servicer = s_p.servicer
AND ca.product = s_p.product
AND ca.product_group = s_p.product_group
AND ca.portfolio = s_p.portfolio
AND ca.channel = s_p.channel
FULL OUTER JOIN adhoc_work.Summary_uy s_uy
ON ca.reporting_period = s_uy.reporting_period
AND ca.state = s_uy.state
AND s_p.state = s_uy.state
AND ca.servicer = s_uy.servicer
AND s_p.servicer = s_uy.servicer
AND ca.product = s_uy.product
AND s_p.product = s_uy.product
AND ca.product_group = s_uy.product_group
AND s_p.product_group = s_uy.product_group
AND ca.portfolio = s_uy.portfolio
AND s_p.portfolio = s_uy.portfolio
AND ca.channel = s_uy.channel
AND s_p.channel = s_uy.channel
WHERE COALESCE(ca.reporting_period,s_p.reporting_period,s_uy.reporting_period) BETWEEN DATE_FORMAT(TIMESTAMPADD(MONTH,-13,NOW(3)),'%Y%m%d') AND DATE_FORMAT(NOW(3),'%Y%m%d')
GROUP BY COALESCE(ca.reporting_period,s_p.reporting_period,s_uy.reporting_period)
,COALESCE(ca.state,s_p.state,s_uy.state)
,COALESCE(ca.servicer,s_p.servicer,s_uy.servicer)
,COALESCE(ca.product,s_p.product,s_uy.product)
,COALESCE(ca.product_group,s_p.product_group,s_uy.product_group)
,COALESCE(ca.portfolio,s_p.portfolio,s_uy.portfolio)
,COALESCE(ca.channel,s_p.channel,s_uy.channel)
,ca.gross
,ca.Costs
,ca.commission
,ca.commissionable
,s_p.WAVG_placed_numerator
,s_p.place_balance
,ca.costs_recovered;

Answer 1

Actually, your query doesn't quite do a full outer join, because a condition like this:
ca.state = s_uy.state
requires that ca.state be matched. That is, the outer join is turned to an inner join.
So, to answer your question more theoretically, the simplest method is probably to generate all the rows by using UNION among the the table and then use left join:
FROM (SELECT reporting_period, . . .
FROM adhoc_work.Cash ca
UNION -- on purpose to remove duplicates
SELECT reporting_period, . . .
FROM adhoc_work.Summary_placed
UNION -- on purpose to remove duplicates
SELECT reporting_period, . . .
FROM adhoc_work.Summary_uy
) x LEFT JOIN
adhoc_work.Cash ca
ON x.reporting_period = ca.reporting_period AND
. . . LEFT JOIN
adhoc_work.Summary_placed s_p
ON x.reporting_period = s_p.reporting_period AND
. . . LEFT JOIN
adhoc_work.Summary_uy s_uy
ON x.reporting_period = s_uy.reporting_period AND
. . .