How to substitute with Comma Separate values in Oracle SQL - sql

Question

I have a scenario like below (Oracle's SQL).
Table:Employee
S.No
Name
Role
1
a
ELE,PLU,OTH
2
b
MAN,DIR
3
c
DIR,FND
4
d
Table: Role_master
Role
Role name
ELE
Electrician
PLU
Plumber
MAN
Manager
DIR
Director
FND
Founder
OTH
Other
With the above tables, i would like to join both and expecting the output like below. Please help on the better way.
S.No
Name
Role
1
a
Electrician,Plumber,Other
2
b
Manager,Director
3
c
Director,Founder
4
d

Answer 1

Here's one option:
sample data in lines #1 - 12; query begins at line #14
split employee.role into rows (i.e. separate values) so that you could join them to role_master.role
aggregate them back (using listagg)
SQL> with
2 employee (sno, name, role) as
3 (select 1, 'a', 'ELE,PLU,OTH' from dual union all
4 select 2, 'b', 'MAN,DIR' from dual
5 ),
6 role_master (role, role_name) as
7 (select 'ELE', 'Electrician' from dual union all
8 select 'PLU', 'Plumber' from dual union all
9 select 'OTH', 'Other' from dual union all
10 select 'MAN', 'Manager' from dual union all
11 select 'DIR', 'Director' from dual
12 )
13 --
14 select e.sno,
15 e.name,
16 listagg(m.role_name, ',') within group (order by column_value) role
17 from employee e cross join
18 table(cast(multiset(select level from dual
19 connect by level <= regexp_count(e.role, ',') + 1
20 ) as sys.odcinumberlist))
21 join role_master m on m.role = regexp_substr(e.role, '[^,]+', 1, column_value)
22 group by e.sno, e.name;
SNO NAME ROLE
---------- ---- ----------------------------------------
1 a Electrician,Plumber,Other
2 b Manager,Director
SQL>

Answer 2

Another solution could use this logic :
First, generate the maximum number of rows needed for the split step (required_rows_v)
Then, make left join between the three data sources like below
Then, use listagg function to re-aggregate rows
With required_rows_v (lvl) as (
select level lvl
from dual
connect by level <= ( select max( regexp_count( e.Role, '[^,]+' ) ) from employee e )
)
select e.SNO,
e.NAME,
listagg(rm.Role_name, ',')within group (order by e.SNo, v.lvl) Role
from employee e
left join required_rows_v v on v.lvl <= regexp_count( e.Role, '[^,]+' )
left join Role_master rm on rm.Role = regexp_substr( e.Role, '[^,]+', 1, v.lvl )
group by e.SNO, e.NAME
demo