Oracle11g 偏移和分组
我有两列“a”和“b”。a列有20条记录，我想从“a”列中选择前10条记录，并将“b”列更新为“c” 然后从a中选择接下来的10条记录，并将列“b”更新为“d”。？ 我怎样才能做到这一点？有可能在其中使用偏移吗？ 我尝试使用分区，但没有太大帮助，然后我想到了偏移量，但我如何循环选择10条记录并更新值Oracle11g 偏移和分组,oracle11g,plsqldeveloper,Oracle11g,Plsqldeveloper,我有两列“a”和“b”。a列有20条记录，我想从“a”列中选择前10条记录，并将“b”列更新为“c” 然后从a中选择接下来的10条记录，并将列“b”更新为“d”。？ 我怎样才能做到这一点？有可能在其中使用偏移吗？ 我尝试使用分区，但没有太大帮助，然后我想到了偏移量，但我如何循环选择10条记录并更新值 A B 1 2 3 4 5 6 我想取A的前三条记录，用C更新B，然后取下三条记录，用D更新B A B 1 C 2 C 3 C 4 D 5 D 6 D 根据您想要如何处理奇数行的情
A B
1
2
3
4
5
6
A B
1 C
2 C
3 C
4 D
5 D
6 D
根据您想要如何处理奇数行的情况—您想要更多的C还是更多的D，您可以使用以下两条合并语句之一更新行：
create table t1 as
select 1 a, cast(null as varchar2(2)) b from dual union all
select 2 a, null b from dual union all
select 3 a, null b from dual union all
select 4 a, null b from dual union all
select 5 a, null b from dual union all
select 6 a, null b from dual;
-- six rows, basic method - for odd rows, there will be a greater number of Ds
merge into t1 tgt
using (select a,
case when rn/cnt <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
commit;
select * from t1;
A B
---------- --
1 C
2 C
3 C
4 D
5 D
6 D
-- six rows, extended method - for odd rows, there will be a greater number of Cs
merge into t1 tgt
using (select a,
case when rn/decode(mod(cnt, 2), 0, cnt, 1, cnt + 1) <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
commit;
select * from t1;
A B
---------- --
1 C
2 C
3 C
4 D
5 D
6 D
insert into t1 (a, b)
values (7, null);
commit;
-- seven rows, basic method - for odd rows, there will be a greater number of Ds
merge into t1 tgt
using (select a,
case when rn/cnt <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
select * from t1;
A B
---------- --
1 C
2 C
3 C
4 D
5 D
6 D
7 D
-- seven rows, extended method - for odd rows, there will be a greater number of Cs
merge into t1 tgt
using (select a,
case when rn/decode(mod(cnt, 2), 0, cnt, 1, cnt + 1) <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
select * from t1;
A B
---------- --
1 C
2 C
3 C
4 C
5 D
6 D
7 D
drop table t1;
merge into t1 tgt
using (select a,
case when rn/cnt <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
merge into t1 tgt
using (select a,
case when rn/decode(mod(cnt, 2), 0, cnt, 1, cnt + 1) <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
create table t1 as
select 1 a, cast(null as varchar2(2)) b from dual union all
select 2 a, null b from dual union all
select 3 a, null b from dual union all
select 4 a, null b from dual union all
select 5 a, null b from dual union all
select 6 a, null b from dual;
-- six rows, basic method - for odd rows, there will be a greater number of Ds
merge into t1 tgt
using (select a,
case when rn/cnt <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
commit;
select * from t1;
A B
---------- --
1 C
2 C
3 C
4 D
5 D
6 D
-- six rows, extended method - for odd rows, there will be a greater number of Cs
merge into t1 tgt
using (select a,
case when rn/decode(mod(cnt, 2), 0, cnt, 1, cnt + 1) <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
commit;
select * from t1;
A B
---------- --
1 C
2 C
3 C
4 D
5 D
6 D
insert into t1 (a, b)
values (7, null);
commit;
-- seven rows, basic method - for odd rows, there will be a greater number of Ds
merge into t1 tgt
using (select a,
case when rn/cnt <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
select * from t1;
A B
---------- --
1 C
2 C
3 C
4 D
5 D
6 D
7 D
-- seven rows, extended method - for odd rows, there will be a greater number of Cs
merge into t1 tgt
using (select a,
case when rn/decode(mod(cnt, 2), 0, cnt, 1, cnt + 1) <= 0.5 then 'C'
else 'D'
end new_b
from (select a,
row_number() over (order by a) rn,
count(*) over () cnt
from t1)) src
on (tgt.a = src.a)
when matched then
update set tgt.b = src.new_b;
select * from t1;
A B
---------- --
1 C
2 C
3 C
4 C
5 D
6 D
7 D
drop table t1;
你需要用一些样本数据和你期望的输出更新你的问题。好吧，在你的原始逻辑中，你有20行，前10行你希望你的B列值是C，其余的你希望值是D。在你的样本数据中，有6行，你想要3个C和3个D。实际的要求是，我有X行，我希望前半行有B=C，其余的是D？是的，完全正确…如果我们不进入奇数和偶数，并生成一个序列，假设给出C，D，e的输出，这必须在一个过程中完成。。。哪一个会进一步用c更新A列的前3条记录，然后用d更新下3条记录…依此类推，直到A中的所有记录都有相应的B…那么你建议我们怎么做呢？如果我更新t1集合B=c，其中A在从t1中选择A，其中B为空，只获取前3行，并将其保持在循环中以更新A的其余行？但是此查询不起作用，因为它表示缺少右键