Oracle SQL - break 1 row into 2 rows - sql

Question

I have the following table:
create table members
(
member_number number(10),
title varchar2(5),
lastname varchar2(30),
personal_email varchar2(20),
work_email varchar2(20)
)
with the data
Insert into MEMBERS
(MEMBER_NUMBER, TITLE, LASTNAME, PERSONAL_EMAIL, WORK_EMAIL)
Values
(11, 'MR', 'Dore', 'personal#email.com', 'work#email.com');
COMMIT;
select member_number, title, lastname,
decode (:pi_email,
'Work', work_email, personal_email) destination
from members
where member_number = 11
and decode (:pi_email,
'Work', work_email, personal_email) is not null
union
select member_number, title, lastname, work_email
from members
where member_number = 11
and :pi_email = 'Both'
and work_email is not null
Question:
Is it possible to re-write the code using 1 select and not using a UNION.
I want to be able to pass pi_email value of 'Work' and select the work_email, alternatively select the personal_email, however if I pass 'Both' I want to select both email addresses in 2 lines/rows.

Answer 1

If I understand correctly, you can unpivot the data and then use a where clause. In Oracle 12C+, you can do this using a lateral join:
select m.member_number, m.title, m.lastname, e.email
from members m cross join lateral
(select 'work' as which, m.work_email as email from dual union all
select 'personal' as which, m.personal_email from dual
) e
where :pi_email in (e.which, 'both');
In earlier versions of Oracle, you can do something similar with union all in the from clause.

Answer 2

How about a CTE with additional column (what in my example, which tells what kind of an e-mail address is that)?
Sample data:
SQL> select * from members;
MEMBER_NUMBER TITLE LASTNAME PERSONAL_EMAIL WORK_EMAIL
------------- ----- ---------- -------------------- --------------------
11 MR Dore personal#email.com work#email.com
Query (runs in SQL*Plus) - fetch work e-mail address:
SQL> set ver off
SQL> with data as
2 (select 'P' what, member_number, title, lastname, personal_email email
3 from members
4 union all
5 select 'W' what, member_number, title, lastname, work_email email
6 from members
7 )
8 select member_number,
9 title,
10 lastname,
11 email
12 from data
13 where member_number = &pi_memnum
14 and (what = '&&pi_email' or '&&pi_email' is null);
Enter value for pi_memnum: 11
Enter value for pi_email: W
MEMBER_NUMBER TITLE LASTNAME EMAIL
------------- ----- ---------- --------------------
11 MR Dore work#email.com
Another example, which fetches both e-mail addresses (what is left NULL):
SQL> undefine pi_email
SQL>
SQL> /
Enter value for pi_memnum: 11
Enter value for pi_email:
MEMBER_NUMBER TITLE LASTNAME EMAIL
------------- ----- ---------- --------------------
11 MR Dore personal#email.com
11 MR Dore work#email.com
SQL>
If you don't use SQL*Plus, the last two lines (i.e. the where clause) would be
where member_number = :pi_memnum
and (what = :pi_email or :pi_email is null);