JOIN句を使用して、2つ以上のテーブルのコンテンツを結合できます。 このトピックでは、JOIN句の構文と例について説明します。
join_table:
table_reference [INNER] JOIN table_factor [join_condition]
| table_reference {LEFT|RIGHT|FULL} [OUTER] JOIN table_reference join_condition
| table_reference CROSS JOIN table_reference [join_condition])
table_reference:
table_factor
| join_table
table_factor:
tbl_name [alias]
| table_subquery alias
| ( table_references )
join_condition:
ON expression 例：
この例では、FROM句の2つのサブクエリを結合して、2つのイベントの販売済みチケットと未販売チケットの数を照会します。
select catgroup1, sold, unsold
from
(select catgroup, sum(qtysold) as sold
from category c, event e, sales s
where c.catid = e.catid and e.eventid = s.eventid
group by catgroup) as a(catgroup1, sold)
join
(select catgroup, sum(numtickets)-sum(qtysold) as unsold
from category c, event e, sales s, listing l
where c.catid = e.catid and e.eventid = s.eventid
and s.listid = l.listid
group by catgroup) as b(catgroup2, unsold)
on a.catgroup1 = b.catgroup2
order by 1;