子查询多行oracle

Question

我有一个包含这些值的表格：

╔════╦═══════════════╗
║ ID ║     TYPE      ║
╠════╬═══════════════╣
║  1 ║ FUEL PUMP     ║
║  2 ║ FIRE ALARM    ║
║  3 ║ FIRE PUMP     ║
║  4 ║ SAFETY SHOWER ║
╚════╩═══════════════╝

(query is: SELECT DISTINCT TYPE FROM EQUIPMENT)

返回以下内容的查询：

╔═════════════╦══════════════╗
║    Room     ║ Equipment ID ║
╠═════════════╬══════════════╣
║ Locker Room ║            1 ║
║ Hallway     ║            1 ║
║ Foyer       ║            2 ║
║ Office 1    ║            3 ║
║ Office 2    ║            2 ║
╚═════════════╩══════════════╝

我试图通过在生成上表的查询的SELECT和WHERE语句中使用子查询来显示EQUIPMENT.TYPE字段。但是，我得到了：ORA-01427: single-row subquery returns more than one row 01427. 00000 - "single-row subquery returns more than one row"。我认为这是因为EQUIPMENT ID值不止一次返回。

是否可以通过加入来执行此操作？

Answer 1

select room, type
from equipment join rooms 
on rooms.equipment_id = equipment.id

假设另一个表名为ROOMS。