我有树表
ID A
-----------
1 10
ID B
-----------
1 20
2 30
ID C
-----------
2 40
3 50
有人可以告诉我们如何制作视图或查询这样的打印件吗?
ID A B C R (A + B - C)
-----------------------------------
1 10 20 0 30
2 0 30 40 -10
3 0 0 50 -50
提前致谢。
答案 0 :(得分:8)
据我所知,MySql中没有完整的外连接。因此,要执行您需要的操作,您应该在派生表中获取不同的ID并离开连接原始表:
select ids.id,
ifnull(table1.A, 0) A,
ifnull(table2.B, 0) B,
ifnull(table3.C, 0) C,
ifnull(table1.A, 0) + ifnull(table2.B, 0) - ifnull(table3.C, 0) R
from
(
select id
from table1
union
select id
from table2
union
select id
from table3
) ids
left join table1
on ids.id = table1.id
left join table2
on ids.id = table2.id
left join table3
on ids.id = table3.id
答案 1 :(得分:0)
select coalesce(a.Id, b.Id, c.Id) ID,
case when a.A > 0 then a.A else 0 end,
case when b.B > 0 then b.B else 0 end,
case when c.C > 0 then c.C else 0 end,
ifnull(a.A, 0) + ifnull(b2.B, 0) - ifnull(c.C, 0) R
from tableA a
right outer join tableB b on a.id = b.id
right outer join tableC c on b.id = c.id;
答案 2 :(得分:-1)
试试这个
select t1.ID, t1.A,t2.B,t3.C,t1.A+t2.B-t3.C as R
from tableA t1
full outer join tableB t2 on t1.id =t2.id
full outer join tableC t3 on t1.id =t3.id