Question

我有两个表（T1，T2）通过外键列（B，C）相互连接。

T1

C   B   A
11  1   123
12  2   123
13  3   123
14  4   222
15  5   222
16  6   333

T2

A2  B2  C2  D
    1   11  25/4/1972
    2   12  2/11/1982
    3   13  4/6/2000
    4   14  2/7/1992
    5   15  14/2/2010
    6   16  6/3/1999

我需要根据D（T2）列中最早的日期从A值（T1）更新A2值（T2），得到以下结果：

T2

A2  B2  C2  D
123 1   11  25/4/1972
    2   12  2/11/1982
    3   13  4/6/2000
222 4   14  2/7/1992
    5   15  14/2/2010
333 6   16  6/3/1999

show resulet

Answer 1

这远非 smart＆amp;很好的解决方案，但是 - 可能没问题，直到有人发布更好的东西。

其他人的测试案例（节省一些时间，因为Omar选择不这样做）：

create table t1 (c number, b number, a number);
create table t2 (a2 number, b2 number, c2 number, d date);
insert into t1
  select 11, 1, 123 from dual union
  select 12, 2, 123 from dual union
  select 13, 3, 123 from dual union
  select 14, 4, 222 from dual union
  select 15, 5, 222 from dual union
  select 16, 6, 333 from dual;
insert into t2 (b2, c2, d) 
  select 1, 11, date '1972-04-25' from dual union
  select 2, 12, date '1982-11-02' from dual union
  select 3, 13, date '2000-06-04' from dual union
  select 4, 14, date '1992-07-02' from dual union
  select 5, 15, date '2010-02-14' from dual union
  select 6, 16, date '1999-03-06' from dual;

首先更新每一行，然后删除不必要的值：

SQL> update t2 set
  2    t2.a2 = (select t1.a
  3             from t1
  4             where t1.b = t2.b2
  5               and t1.c = t2.c2
  6            );

6 rows updated.

SQL> update t2 set
  2    t2.a2 = (select distinct
  3               case when min(x.d) over (partition by x.a2) = t2.d then t2.a2
  4                    else null
  5               end
  6             from t2 x
  7             where x.a2 = t2.a2
  8            );

6 rows updated.

SQL> select * from t2;

        A2         B2         C2 D
---------- ---------- ---------- ----------
       123          1         11 25.04.1972
                    2         12 02.11.1982
                    3         13 04.06.2000
       222          4         14 02.07.1992
                    5         15 14.02.2010
       333          6         16 06.03.1999

6 rows selected.

SQL>

Answer 2

假设日期是唯一的（如您的示例所示），您可以执行以下操作：

update t2
    set t2.a2 = (select t1.a from t1 where t1.b = t2.b2)
    where t2.d = (select min(tt2.d)
                  from t1 join
                       t2 tt2
                       on tt2.b2 = t1.b
                  group by t1.a
                 );

如果您有重复项，可以将where更改为：

where (t2.b2, t2.d) = (select min(tt2.b2) keep (dense_rank first over order by tt2.d), min(tt2.d)
                       from t1 join
                            t2 tt2
                            on tt2.b2 = t1.b
                       group by t1.a
                      )

表oracle depand更新最旧日期的值

2 个答案: