Combining UNION and LIMIT operations in MySQL query

Question

I have a Jobs and a Companies table, and I want to extract 20 jobs that meet the following criteria:

1. Jobs only from two (2) named companies
2. There can at most be 10 jobs per company

I have tried the following SELECT with UNION DISTINCT , but the problem is that the LIMIT 0,10 applies to the whole result set. I want it to apply to each of the companies.

If there aren't 10 jobs per company, then the query should return all the jobs it finds.

SELECT c.name, j.title, j.`desc`, j.link 
  FROM jobs_job j
INNER JOIN companies_company c ON j.company_id = c.id
WHERE c.name IN ('Company1')
UNION DISTINCT
SELECT c.name, j.title, j.`desc`, j.link 
  FROM jobs_job j
INNER JOIN companies_company c ON j.company_id = c.id
WHERE c.name IN ('Company2')
ORDER by name, title
LIMIT 0,10

I am new to MySQL, so realise there may be a smarter way to do this instead of with UNION, so any suggestions for improvements are definitely welcome.

Answer 1

Quoting the docs ,

To apply ORDER BY or LIMIT to an individual SELECT, place the clause inside the parentheses that enclose the SELECT:

(SELECT a FROM t1 WHERE a=10 AND B=1 ORDER BY a LIMIT 10)
UNION
(SELECT a FROM t2 WHERE a=11 AND B=2 ORDER BY a LIMIT 10);

Answer 2

Improving on Alex's answer and based on Joe's observation, the following should work in SQLite:

SELECT * FROM 
(SELECT a FROM t1 WHERE a=10 AND B=1 ORDER BY a LIMIT 10)
UNION
(SELECT a FROM t2 WHERE a=11 AND B=2 ORDER BY a LIMIT 10);

Answer 3

@bioye answer needed a slight modification for me on SQLite.

SELECT * FROM 
(SELECT a FROM t1 WHERE a=10 AND B=1 ORDER BY a LIMIT 10)
UNION
SELECT * FROM 
(SELECT a FROM t2 WHERE a=11 AND B=2 ORDER BY a LIMIT 10);

Answer 4

In Teradata we can't use union with top queries as it, if you do you get an error, which needs to be tweaked as shown below. Adding solution for Teradata users.