如何将两个表与两个表的ID联合起来？

Question

好的，我有四张桌子：

表1：“f_withholdings”

表2：“f_wh_list”

表3：“f_rpayments”

表4：“f_rp_list”

表1和表2通过wh_id字段相互连接 表3和表4由rp_id连接，如图所示。

我想将两个表合并为一个，例如：

SELECT
`wh_list_id`,
`wh_name` AS `name`,
`wh_list_date` AS `date`,
`wh_list_amount` AS `amount`,
`wh_list_pending` AS `pending`,
`wh_list_comment` AS `comment`
FROM
`f_wh_list` LEFT JOIN `f_withholdings` ON `f_wh_list`.`wh_id` = `f_withholdings`.`wh_id`

UNION ALL

SELECT
`rp_list_id`,
`rp_name` AS `name`,
`rp_list_date` AS `date`,
`rp_list_amount` AS `amount`,
`rp_list_pending` AS `pending`,
`rp_list_comment` AS `comment`
FROM `f_rp_list` LEFT JOIN `f_rpayments` ON `f_rp_list`.`rp_id` = `f_rpayments`.`rp_id`

我得到了这个：

结果表中第一个SELECT wh_list_id只有一个id字段，但没有rp_list_id

我想在结果表中有两个id，如下所示：

谢谢！

Answer 1

只需选择null作为每个列中缺少的列。

SELECT
`wh_list_id`,
null AS `rp_list_id`,
`wh_name` AS `name`,
`wh_list_date` AS `date`,
`wh_list_amount` AS `amount`,
`wh_list_pending` AS `pending`,
`wh_list_comment` AS `comment`
FROM
`f_wh_list` LEFT JOIN `f_withholdings` ON `f_wh_list`.`wh_id` = `f_withholdings`.`wh_id`

UNION ALL

SELECT
null as `wh_list_id`,
`rp_list_id`,
`rp_name` AS `name`,
`rp_list_date` AS `date`,
`rp_list_amount` AS `amount`,
`rp_list_pending` AS `pending`,
`rp_list_comment` AS `comment`
FROM `f_rp_list` LEFT JOIN `f_rpayments` ON `f_rp_list`.`rp_id` = `f_rpayments`.`rp_id`

Answer 2

只需为每个查询添加一个相应的空列（UNIONs在列位置之外工作，它们不关心名称或别名）：

SELECT
`wh_list_id`,
NULL,
...

SELECT
NULL,
`rp_list_id`,
...

将ID保存在一列中可能稍微好一些，并添加一个字段来指定id来自哪个查询（例如SELECT 'wh_list', ...）。