How to divide result in 80/20

Question

Hi
I have bit different requirement.
I have table A which has 1000 records.
Now I was insert 80% of record from table A into Table B80
and remaining 20% in C20
How can I do that.

Answer 1

A more generic way using a single insert statement would be something like...
insert all
  when grp = 0 then
    into b80 (... columns ...)
    values (... columns ...)
  when grp = 1 then
    into c20 (... columns ...)
    values (... columns ...)
select ... columns ...
      ,case when row_number() over (order by 1) / count(*) over () <= 0.8 then 0 else 1 end as grp
from ae.g.
SQL> create table emp80 as select * from emp where 1=0;
Table created.
SQL> create table emp20 as select * from emp where 1=0;
Table created.
SQL> select * from emp80;
no rows selected
SQL> select * from emp20;
no rows selected
SQL> ed
Wrote file afiedt.buf
  1  insert all
  2    when grp = 0 then
  3      into emp80 (empno, ename, job, mgr, hiredate, sal, comm, deptno)
  4      values (empno, ename, job, mgr, hiredate, sal, comm, deptno)
  5    when grp = 1 then
  6      into emp20 (empno, ename, job, mgr, hiredate, sal, comm, deptno)
  7      values (empno, ename, job, mgr, hiredate, sal, comm, deptno)
  8  select empno, ename, job, mgr, hiredate, sal, comm, deptno
  9        ,case when row_number() over (order by 1) / count(*) over () <= 0.8 then 0 else 1 end as grp
10* from emp
SQL> /
14 rows created.
SQL> select * from emp80;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
11 rows selected.
SQL> select * from emp20;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
SQL>