Question

我有桌子：T1 (ID BIGINT, NAME NVARCHAR(1000))

数据：

select * from T1
1, AAA
2, BBB
3, CCC
4, DDD

RELATIONS_T（ID, T1_ID1,T1_ ID2）表格保存ID表格T1之间的关系。

SELECT * 
FROM RELATIONS_T

输出：

ID, T1_ID1,T1_ ID2
1,    1,   2

在此表1中连接到2

RELATIONS_LOG_TABLE（ID, OLD_ID, NEW_ID, OLD_STUFF_ID, NEW_STUFF_ID）列OLD_STUFF_ID和NEW_STUFF_ID对我的问题不重要。

Select ID, OLD_ID, NEW_ID 
from RELATIONS_LOG_TABLE

输出：

ID, OLD_ID, NEW_ID
1, 1, 3
2, 2, 4

这意味着1变为3，2变为4

如何从表RELATIONS_LOG_TABLE和RELATIONS_T检查1和2之间是否存在连接，并在表RELATIONS_T 3,4中手动输入。

Answer 1

以下语句将插入元组

3,2 (1 replaced by 3)
1,4 (2 replaced by 4)
3,4 (both replaced)

insert into relations_t (id1, id2)
  select coalesce(rep1.new_id, id1), coalesce(rep2.new_id, id2)
  from relations_t r
  left join relations_log_table rep1 on rep1.old_id = r.id1
  left join relations_log_table rep2 on rep2.old_id = r.id2
  where rep1.id is not null or rep2.id is not null;

如果你只想要＆＃34;最好的＆＃34;记录（如果是这种情况则更换，否则更换一个），您必须根据替换次数获得最高记录。

insert into relations_t (id1, id2)
  select top(1) coalesce(rep1.new_id, id1), coalesce(rep2.new_id, id2)
  from relations_t r
  left join relations_log_table rep1 on rep1.old_id = r.id1
  left join relations_log_table rep2 on rep2.old_id = r.id2
  where rep1.id is not null or rep2.id is not null
  order by case when rep1.id is not null and rep2.id is not null then 0 else 1 end;

如何使用表中的新ID将关系从一个表转移到另一个表

1 个答案: