Miscellany

explain SELECT * FROM job JOIN companies ON companies.companyid = job.companyid JOIN job_postings ON (job.jobid = job_postings.jobid) WHERE job.jobid IN (16189,16188);
 
+--------------+-------+-------------------+---------+---------+-------+------+-------------+
| table        | type  | possible_keys     | key     | key_len | ref   | rows | Extra       |
+--------------+-------+-------------------+---------+---------+-------+------+-------------+
| job          | const | PRIMARY,companyid | PRIMARY |       4 | const |    2 |             |
| companies    | const | PRIMARY           | PRIMARY |       4 | const |    2 |             |
| job_postings | ref   | PRIMARY           | PRIMARY |       4 | const |    8 | Using where |
+--------------+-------+-------------------+---------+---------+-------+------+-------------+