sql - 如何根据一列自动备份表的比例？

Question

我想自动备份一个数据库，所以我有两个数据库，一个包含所有数据，另一个包含每个表的比率 - 即 20% - 基于列。

Answer 1

这是我的第一次尝试。

create table t1 (
id integer primary key,
val integer not null);

create table t2 (
id integer primary key,
val integer not null);

insert into t1 values (1,1000);
insert into t1 values (2,1000);
insert into t1 values (3,1000);
insert into t1 values (4,1000);
insert into t1 values (5,1000);
insert into t1 values (6,1000);
insert into t1 values (7,1000);
insert into t1 values (8,1000);
insert into t1 values (9,1000);
insert into t1 values (10,1000);
insert into t1 values (11,1000);

insert into t2
select id, val
from t1
where (val >= 1000) 
  and (rownum <= cast((0.2 * (select count(*) from t1)) as integer));