SELECT CI.NAME
FROM COUNTRY CO
JOIN CITY CI ON CI.CountryCode = CO.CODE
WHERE CO.CONTINENT = 'Africa';
SELECT
xxx,
p1.NAME as p1name,
p2.NAME as p2name
FROM Table1
LEFT JOIN Table2 AS p1 ON Table1.worker1 = p1.ID
LEFT JOIN Table2 AS p2 ON Table1.worker2 = p2.ID
WHERE ...
SELECT
select_list
FROM t1
INNER JOIN t2 ON join_condition1
INNER JOIN t3 ON join_condition2
...;