Convert a piece of SQL into an Oracle function - sql

Question

My table "COMMA_SEPERATED" looks something like this
ID NAME CITY
--- ---- -----------------------------
1 RAJ CHENNAI, HYDERABAD, JABALPUR
2 SAM BHOPAL,PUNE
I want to separate each City as a new record so my SQL is: (working fine)
SELECT id, TRIM(CITY_NEW)
FROM COMMA_SEPERATED, xmltable
(
'if (contains($X,",")) then ora:tokenize($X,"\,") else $X'
passing city AS X
columns CITY_NEW varchar2(4000) path '.'
);
I want to convert this piece of SQL into a function so that i can simply call the function like this
SELECT id, split_function(city) FROM COMMA_SEPERATED
Output:
1 CHENNAI
1 HYDERABAD
1 JABALPUR
2 BHOPAL
2 PUNE
Can anyone help on how to do that? I am very new to PL/SQL.

Answer 1

The query you're trying to get to:
SELECT id, split_function(city) FROM COMMA_SEPERATED
won't work, because you're trying to return multiple rows for each source row. You have to make it a bit more complicated than that unfortunately.
If the goal is to hide the splitting mechanism then the closest I can think of is to create a function which returns a collection of strings, which could be pipelined:
create or replace function split_function (p_string varchar2)
return sys.odcivarchar2list pipelined as
begin
for r in (
select result
from xmltable (
'if (contains($X,",")) then ora:tokenize($X,"\,") else $X'
passing p_string as x
columns result varchar2(4000) path '.'
)
)
loop
pipe row (trim(r.result));
end loop;
end split_function;
/
Your proposed call would then give you one row per ID with a collection:
select id, split_function(city) from comma_seperated;
ID SPLIT_FUNCTION(CITY)
---------- -----------------------------------------------------------------
1 ODCIVARCHAR2LIST('CHENNAI', 'HYDERABAD', 'JABALPUR')
2 ODCIVARCHAR2LIST('BHOPAL', 'PUNE')
which isn't quite what you want; but you can use a table collection expression and cross-join to convert into multiple rows instead:
select cs.id, t.column_value as city
from comma_seperated cs
cross join table(split_function(cs.city)) t;
ID CITY
---------- ------------------------------
1 CHENNAI
1 HYDERABAD
1 JABALPUR
2 BHOPAL
2 PUNE
db<>fiddle demo.
That isn't as simple as you hoped for, but is arguably still better than cross-joining to the xmltable(), particularly if you want to reuse that splitting logic/function in multiple places, as well as hide the details of how the split is done - which would let you change the mechanism easily if you wanted to, e.g. to use a more common regular expression to do the splitting.

Answer 2

Apart what #Alex showed, you can also create an object and get the object returned via function. See below:
--Created an object to hold your result columns
create or replace type Obj IS OBJECT (id number, city varchar2(20));
/
--Table of object
create or replace type var_obj is table of Obj;
/
--Function with return as with Object type.
create or replace function splt_fnct
return var_obj
as
var var_obj:=var_obj();
begin
Select obj(col,col1)
bulk collect into var
from (
Select distinct col , regexp_substr(col1,'[^,]+',1,level) col1
from tbl
connect by regexp_substr(col1,'[^,]+',1,level) is not null
order by 1);
return var;
end;
/
--Selecting result
select * from table(splt_fnct);
Edit: I was trying with #Alex solution and got some error as shown below:
create or replace function splt_fnct(input_strng varchar2)
return var_obj
as
var var_obj:=var_obj();
begin
Select obj(col,col1)
bulk collect into var
from (
select tbl.col, t.rslt --<--This column name should the same as used in colmns clause in the below query. Its giving error "invalid column". How to handle this case.
FROM tbl, xmltable
(
'if (contains($X,",")) then ora:tokenize($X,"\,") else $X'
passing col1 AS X
columns input_strng varchar2(4000) path '.'
) t
);
return var;
end;
/
Correction as per #Alex suggestion:
create or replace function splt_fnct(input_strng varchar2)
return var_obj
as
var var_obj:=var_obj();
begin
select obj(tbl.col, t.rslt)
bulk collect into var
FROM tbl, xmltable
(
'if (contains($X,",")) then ora:tokenize($X,"\,") else $X'
passing input_strng AS X
columns rslt varchar2(4000) path '.'
) t;
return var;
end;
/