Question

我有3张桌子：

地址

id, address, city, zipcode

人（1500条记录）

id, address_id, firtname, lastname, sex, title

建筑物（100条记录）

id, address_id, name, type_of_building

多人/建筑物共用同一地址。我需要列出所有地址及其人员或建筑信息。所以，我的查询应该返回总共1600条记录。

我需要编写哪种查询来检索此信息？

Answer 1

由于您需要来自两个不同数据集的所有记录，因此您需要使用INNER JOIN和UNION。这样的事情可能有用：

SELECT p.id, p.firstname, p.lastname, p.sex, p.title, a.address, a.city, a.zipcode
FROM persons p
  INNER JOIN addresses a on a.id = p.address_id

UNION ALL

SELECT b.id, b.name, '', '', b.type_of_building, a.address, a.city, a.zipcode
FROM buildings b
  INNER JOIN addresses a on a.id = b.address_id

Answer 2

这将是 UNION ，因为您要合并两个不同数据集的结果。为了获得统一信息，您需要使用相同的字段，因此我将使用示例：

(SELECT address_id, firstname AS value1, lastname AS value2, sex AS value3, title AS value4 FROM persons)
    UNION
(SELECT address_id, name AS value1, type_of_building AS value2, 0 AS value3, 0 AS value4 FROM buildings)

MySQL JOIN在三个表上

2 个答案: