sql how to combine three queries from two tables into one query

Question

i have the following two tables:

Table1

id  name
---------
A3  B2
A3  B400
A5  B100
A7  B200
A8  B6
A8  B2
A8  B3

and

Answer 1

These requirements are confusing enough it might be worth a re-assessment of your data model. I think the UNION solution is your best bet possibly modified to use UNION ALL for efficiency.

I did put together a mutex based hack that likely has as many subtle problems as any of the other queries on this page.

select
  coalesce(t2.id, t1.name) AS ID,
  coalesce(t2.company, t1.name) AS Company,
  if(isnull(t2.id), 'NOT FOUND', 'FOUND') as Status
from (select 0 as mutex union select 1) as m
left join table1 as t1 on 1 = 1
left join table2 as t2 on t1.name = t2.name or (t1.id = t2.id and mutex)
group by coalesce(t2.id, t1.name)

That said, please test these queries carefully and look over your data and results. There's a whole lot of room for error depending on your input data.