JOIN

JOINでテーブル同士を結合する。

7.2. テーブル式

postgresdb1=# SELECT * FROM profile;
 id |  name  | address
----+--------+---------
  1 | Taro   | Tokyo
  2 | Jiro   | Osaka
  3 | Saburo | Nagoya
(3 行)

postgresdb1=# SELECT * FROM orders;
 id | profile_id | product  | amount
----+------------+----------+--------
  1 |          1 | Pen      |     10
  2 |          1 | Notebook |      5
  3 |          2 | Pencil   |      7
(3 行)

postgresdb1=# SELECT p.name, p.address, o.product, o.amount
FROM profile AS p
JOIN orders AS o ON p.id = o.profile_id;
 name | address | product  | amount
------+---------+----------+--------
 Taro | Tokyo   | Pen      |     10
 Taro | Tokyo   | Notebook |      5
 Jiro | Osaka   | Pencil   |      7
(3 行)

postgresdb1=#

idが共通なので、idを基に結合。
profileとordersを結合できた。