MYSQL Using Union to combine two queries

Question

My first query looks as below

SELECT a.name, b.desc, T3.desc1 as Output
FROM table1 a INNER JOIN
     table2 b
     ON a.id = b.id
INNER JOIN (
  SELECT b2.id, b2.status,  MAX(b2.created_time) as max_time
  FROM oac.qualys_scan b2
  GROUP BY b2.id  ,  b2.qualys_type
  ) t on t.id = a.id
      AND  t.status=b.status
      AND t.max_time = b.created_time
INNER JOIN table3 T3 on b.tid = T3.tid
WHERE b.status = 'FAIL'
AND b.type = 'Type1'

My second query looks as below

SELECT a.name, b.desc, T4.desc2 as Output
FROM table1 a INNER JOIN
     table2 b
     ON a.id = b.id
INNER JOIN (
  SELECT b2.id, b2.status,  MAX(b2.created_time) as max_time
  FROM oac.qualys_scan b2
  GROUP BY b2.id  ,  b2.qualys_type
  ) t on t.id = a.id
      AND  t.status=b.status
      AND t.max_time = b.created_time
INNER JOIN table4 T4 on b.tid = T4.tid
WHERE b.status = 'FAIL'
AND b.type = 'Type2'

In my final result I want Output column which will have values either from T3.desc1 or T4.desc2 How can I use UNION to combine both queries into a single query?

Answer 1

just put UNION ALL between the queries. Youll have to alias the columns

Answer 2

Do this:

Query1 UNION Query2; -- for union without duplicates (the set union as in maths)

OR

Query1 UNION ALL Query2; -- for union with duplicates

So it should be:

SELECT a.name, b.desc, T3.desc1 as Output
FROM table1 a INNER JOIN
     table2 b
     ON a.id = b.id
INNER JOIN (
  SELECT b2.id, b2.status,  MAX(b2.created_time) as max_time
  FROM oac.qualys_scan b2
  GROUP BY b2.id  ,  b2.qualys_type
  ) t on t.id = a.id
      AND  t.status=b.status
      AND t.max_time = b.created_time
INNER JOIN table3 T3 on b.tid = T3.tid
WHERE b.status = 'FAIL'
AND b.type = 'Type1'

UNION

SELECT a.name, b.desc, T4.desc2 as Output
FROM table1 a INNER JOIN
     table2 b
     ON a.id = b.id
INNER JOIN (
  SELECT b2.id, b2.status,  MAX(b2.created_time) as max_time
  FROM oac.qualys_scan b2
  GROUP BY b2.id  ,  b2.qualys_type
  ) t on t.id = a.id
      AND  t.status=b.status
      AND t.max_time = b.created_time
INNER JOIN table4 T4 on b.tid = T4.tid
WHERE b.status = 'FAIL'
AND b.type = 'Type2';