Help to get the logic

Question

Hi, I have a table with below data
TableA
id   email
1   [email protected],bbb@abc,com,[email protected]
1   [email protected],[email protected],[email protected]
2   [email protected],[email protected]
2   [email protected],[email protected],[email protected]
now this email column if of 4000 chars.
the requirement is to take the distinct of the email.
i.e i want the output to be
1 [email protected]
1 [email protected]
1 [email protected]
1 [email protected]
1 [email protected]
2 [email protected]
2 [email protected]
2 [email protected]
can some one plz give suggestions how to implement this?

Answer 1

You could try benchmarking this:
WITH
  tbl AS (
    SELECT 1 id,'[email protected],bbb@abc,[email protected]' email FROM dual UNION ALL
    SELECT 1 id,'[email protected],[email protected],[email protected]' email FROM dual UNION ALL
    SELECT 2 id,'[email protected],[email protected]' email FROM dual UNION ALL
    SELECT 2 id,'[email protected],[email protected],[email protected]' email FROM dual),
number_list as (
   select rownum num
   from   dual
   connect by
     level <= (select max(length(email)-length(replace(email,','))) + 1 from tbl))
select
  id,
  substr(
    ','||email||',',
    instr(
      ','||email||',',
      ,1
      ,num)+1,
    instr(
      ','||email||',',
      1,
      num+1)-
    instr(
      ','||email||',',
      ',',1
      num)-1)
from
  tbl,
  number_list
where
  num <= length(email)-length(replace(email,','))+1Works by generating a list of integers from 1 to the maximum number of email addresses in any row (which is optionally really -- you could just generate a list from one to a reasonably large number), joining to the original table and pulling the string between the nth pair of commas.