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

There's something unclear about your queries, because they shouldn't execute as you've shown them (due to select containing non-aggregates not in group by). But based on your explanation of what you're trying to do...

You could use outer joins and then use case logic and/or coalesce to determine which value to use in each case.

SELECT DISTINCT
       coalesce(t2_id.id, t2_name.id, t1.name) as ID
     , coalesce(t2_id.company, t2_name.company, t1.name) as Conpany
     , case when t2_id.id is not null or t2_name.name is not null
            then 'FOUND'
            else 'NOT FOUND'
       end status
  FROM           table1 t1
       LEFT JOIN table2 t2_id
              ON t1.id = t2_id.id
       LEFT JOIN table2 t2_name
              ON t1.name = t2_name.name

Note that I used DISTINCT to make sure the exact same row doesn't appear multiple times; but this may return multiple rows for an ID (with different Company values) depending on the data. I couldn't quite tell what was intended because the uses of DISTINCT and GROUP BY in the three queries as posted in the question didn't seem to add up for me.