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:

Jobs only from two (2) named companies
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.

user_1414651 · Answer

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);

user_7353562 · Answer

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.

Combining UNION and LIMIT operations in MySQL query

3 Answers