How to put comma separated values to a column in oracle - sql

Question

I have a JSON response and after processing the response my output looks like this :
column_variable := 'col1,col2,col3';
data_clob :=
"2017-10-14,abc,1,
2019-10-13,abc,12,
2019-10-12,abc,,
"
;
as the original response was having escape characters for new line ,data_clob also has been converted accordingly .
How do I convert this comma separated values in oracle table :
My output should look like this :
col1 col2 col3
2017-10-14 abc 1
2019-10-13 abc 12
2019-10-12 abc null
I was looking through similar questions ,but I dont want to use REGEXP_SUBSTR as I dont know the number of columns I will get in the response .
for e.g : column_variable might have 'col1,col2,col3,col4,col5,col6';
I am using oracle 12.1.0.2.0
Please help !

Answer 1

There is very easy way to achieve it using Polymorphic Table Functions (Oracle 18c):
Dynamic CSV to Columns Converter: Polymorphic Table Function Example:
create or replace package csv_pkg as
/* The describe function defines the new columns */
function describe (
tab in out dbms_tf.table_t,
col_names varchar2
) return dbms_tf.describe_t;
/* Fetch_rows sets the values for the new columns */
procedure fetch_rows (col_names varchar2);
end csv_pkg;
and body:
create or replace package body csv_pkg as
function describe(
tab in out dbms_tf.table_t,
col_names varchar2
)
return dbms_tf.describe_t as
new_cols dbms_tf.columns_new_t;
col_id pls_integer := 2;
begin
/* Enable the source colun for reading */
tab.column(1).pass_through := FALSE;
tab.column(1).for_read := TRUE;
new_cols(1) := tab.column(1).description;
/* Extract the column names from the header string,
creating a new column for each
*/
for j in 1 .. ( length(col_names) - length(replace(col_names,',')) ) + 1 loop
new_cols(col_id) := dbms_tf.column_metadata_t(
name=>regexp_substr(col_names, '[^,]+', 1, j),--'c'||j,
type=>dbms_tf.type_varchar2
);
col_id := col_id + 1;
end loop;
return dbms_tf.describe_t( new_columns => new_cols );
end;
procedure fetch_rows (col_names varchar2) as
rowset dbms_tf.row_set_t;
row_count pls_integer;
begin
/* read the input data set */
dbms_tf.get_row_set(rowset, row_count => row_count);
/* Loop through the input rows... */
for i in 1 .. row_count loop
/* ...and the defined columns, extracting the relevant value
start from 2 to skip the input string
*/
for j in 2 .. ( length(col_names) - length(replace(col_names,',')) ) + 2 loop
rowset(j).tab_varchar2(i) :=
regexp_substr(rowset(1).tab_varchar2(i), '[^,]+', 1, j - 1);
end loop;
end loop;
/* Output the new columns and their values */
dbms_tf.put_row_set(rowset);
end;
end csv_pkg;
--function
create or replace function csv_to_columns(
tab table, col_names varchar2
) return table pipelined row polymorphic using csv_pkg;
Then you simply pass:
select *
from csv_to_columns( data_clob, column_variable );

Answer 2

Here's one possible solution for Oracle versions below 18 and maybe 12, not sure... This is not perfect and will create an empty column at the end based on data you provided - extra spaces, commas, etc... This may also create a blank space between the 'SELECT' and the first column in output. All that can be removed later manually or with more coding. I hope this helps, at least in some ways:
SELECT 'SELECT '''||REPLACE(str, chr(10), ''' FROM dual'||chr(10)||'UNION ALL'||chr(10)||'SELECT ''')||''' FROM dual' str
FROM
(
SELECT TRIM(REPLACE(str, ',', ''''||', ''')) str FROM
(
SELECT TRIM(BOTH '"' FROM
'"2017-10-14,abc,1,
2019-10-13,abc,12,
2019-10-12,abc,,"') AS str FROM dual
)
)
/
This will build the select statement that can be cleaned up and executed manually or with dynamic SQL:
SELECT '2017-10-14' col, 'abc' col, '1' col, '' FROM dual
UNION ALL
SELECT '2019-10-13' col, 'abc' col, '12' col, '' FROM dual
UNION ALL
SELECT '2019-10-12' col, 'abc' col, '' col, '' FROM dual
The output of the above select statement:
COL COL_1 COL_2
2017-10-14 abc 1
2019-10-13 abc 12
2019-10-12 abc null