请教需要创建新列一个多表联合查询的问题

[低代码开发平台]

经营活动A表：
BillID FukuanMoney
1 1
投资活动B表
BillID ShoukuanMoney HappenTime
2 2 2
筹资活动C表
BillID ShoukuanMoney OrgnizationID
3 3 3
现在我要将上面三张表合并成下面的一张表，怎么写sql
BillID HappenMoney ActionType（这列是新增的，表示该行数据来自哪个表）
1 1 A
2 2 B
3 3 C
各位大侠怎么写sql

[低代码开发平台]

select BillID，FukuanMoney as HappenMoney from A
union
select BillID，ShoukuanMoney as HappenMoney from B
union
select BillID，ShoukuanMoney as HappenMoney from C
我只能写出这样的，但不知道怎么创建新列，希望大家帮忙

[水族杰纶]

--這樣?描述不清楚
select BillID, HappenMoney =FukuanMoney,ActionType='A' from 经营活动A表
union all
select BillID, ShoukuanMoney ,'B' from 投资活动B表
union all
select BillID, ShoukuanMoney,'C' from 筹资活动C表

[低代码开发平台]

select BillID ,FukuanMoney as HappenMoney ,'A' as ActionType from A
union all
select BillID ,ShoukuanMoney,as HappenMoney ,'B' as ActionType from B
union all
select BillID ,ShoukuanMoney,as HappenMoney ,'C' as ActionType from C
搞定了，谢谢。