how to implement multivalued attribute in oracle ?

Question

I want to store more than one Email IDs in the Email id column of a table, as a multivalued attribute. How can I do this in oracle?

Answer 1

The standard way to do this is to define a second table, where you can store one email per row.

Oracle also supports nested tables so a single attribute column can contain multiple values.

Answer 2

The traditional, relational way of doing this would be with a child heap table:

create table emails 
    (id number
     , email_address varchar2(254)
     , constraint em_t23_fk foreign key (id)
                  references t23 (id)
                  )
/

However, you are hinting at a nested table:

create type email_t as object
    (email_address varchar2(254))
/

create type email_nt as table of email_t
/
alter table t23
    add emails email_nt
    nested table emails store as emails_table
/

Here's how it works:

SQL> update t23
  2  set emails = email_nt (email_t('[email protected]')
  3                          , email_t('[email protected]'))
  4  where id = 222
  5  /

1 row updated.

SQL> select * from t23
  2  where id = 222
  3  /

        ID NAME                           DOB
---------- ------------------------------ ---------
EMAILS(EMAIL_ADDRESS)
----------------------------------------------------------------------------------
       222 Sam-I-Am                       06-AUG-02
EMAIL_NT(EMAIL_T('[email protected]'), EMAIL_T('[email protected]'))


SQL>

Edit

The solution with VARRAY is basically the same:

SQL> alter table t23
  2      drop column emails
  3  /

Table altered.

SQL> create type email_va as varray(5) of varchar2(254)
  2  /

Type created.

SQL> alter table t23
  2      add emails email_va
  3  /

Table altered.

SQL> update t23
  2  set emails = email_va ('[email protected]'
  3                        , '[email protected]')
  4  where id = 222
  5  /

1 row updated.

SQL> select t23.name
  2         , e.*
  3  from t23
  4       , table (t23.emails) e
  5  where t23.id = 222
  6  /

NAME                           COLUMN_VALUE
------------------------------ ---------------------------------
Sam-I-Am                       [email protected]
Sam-I-Am                       [email protected]

SQL>