Mysql - 如何在左连接中为整个表起别名

Question

我有一种情况，属性表包含地址 ID（来自 g_addresses 表），而申请人表也包含来自 g_addresses 的地址 ID。 我想将它们连接在一起，但选择表中的所有字段。

我知道使用 'as' 为字段创建别名，但有没有办法为整个表生成别名？

SELECT *
FROM (`reference`)
LEFT JOIN `applicants` ON `applicants`.`id` = `reference`.`applicant_id`
LEFT JOIN `g_people` applicant_person ON `applicant_person`.`id` = `applicants`.`person_id`
LEFT JOIN `g_addresses` applicant_address ON `applicant_address`.`id` = `applicants`.`address_id`
LEFT JOIN `properties` ON `properties`.`id` = `reference`.`property_id`
LEFT JOIN `g_addresses` property_address ON `property_address`.`id` = `properties`.`address_id`
WHERE `reference`.`id` = 4 

这会产生一个只包含一个地址行而不是两个地址行的结果， 返回的行是来自最终连接的行，而不是之前的行，表明它在返回时被覆盖。

Answer 1

我认为您不应该使用掩码引用，例如 * 或 `reference`.*，因为您最终可能会得到一个包含相同列名（id、address_id）的行集。

如果您想从连接表中提取所有列，您可能应该在 SELECT 子句中单独指定它们并为每个列分配一个唯一的别名：

SELECT
  ref.`id` AS ref_id,
  ref.`…`  AS …,
  …
  app.`id` AS app_id,
  …
FROM `reference` AS ref
LEFT JOIN `applicants`  AS app ON app.`id` = ref.`applicant_id`
LEFT JOIN `g_people`    AS ape ON ape.`id` = app.`person_id`
LEFT JOIN `g_addresses` AS apa ON apa.`id` = app.`address_id`
LEFT JOIN `properties`  AS pro ON pro.`id` = ref.`property_id`
LEFT JOIN `g_addresses` AS pra ON pra.`id` = pro.`address_id`
WHERE ref.`id` = 4

Answer 2

更具体地了解您选择的列

SELECT 
  applicant_address.*,
  property_address.*,
  applicants.*,
  applicant_person.*,
  properties.*
FROM (`reference`)
LEFT JOIN `applicants` ON `applicants`.`id` = `reference`.`applicant_id`
LEFT JOIN `g_people` applicant_person ON `applicant_person`.`id` = `applicants`.`person_id`
LEFT JOIN `g_addresses` applicant_address ON `applicant_address`.`id` = `applicants`.`address_id`
LEFT JOIN `properties` ON `properties`.`id` = `reference`.`property_id`
LEFT JOIN `g_addresses` property_address ON `property_address`.`id` = `properties`.`address_id`
WHERE `reference`.`id` = 4