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

I think you can use a query like the following:

SELECT DISTINCT IF(name2 IS NULL, name, ID) AS ID,
       IF(name2 IS NULL, name, Company) AS Company,
       IF(name2 IS NULL, 'NOT FOUND', 'FOUND') AS Status
FROM (       
   SELECT DISTINCT 
          CASE 
             WHEN t1.id = t2.id THEN t1.id 
             WHEN t1.name = t2.name THEN t2.id
             ELSE t1.id
          END AS ID, 
          CASE 
             WHEN t1.id = t2.id THEN t2.company
             WHEN t1.name = t2.name THEN t2.company
             ELSE t1.name
          END AS Company,
          t1.name,
          (SELECT Table2.name
           FROM Table2
           WHERE Table2.name = t1.name LIMIT 1) AS name2
   FROM Table1 AS t1
   LEFT JOIN Table2 AS t2 ON (t1.id = t2.id) OR (t1.name = t2.name)) AS t
ORDER BY ID;

The query use a single LEFT JOIN operation plus a correlated subquery.

Demo here