Split column to multiple columns in PostgreSQL - postgresql

Question

I am going to split one column of my table to multiple columns. The fields are separated by comma and I used the split_part. The problem that I faced is the length of string are not same and after splitting they are located from column 1 to column N.
Column
a,b,c,d,e,f
b,c,e,f
c,d,e,f
my output is:
col1 col2 col3 col4 col5 col6
a b c d e f
b c e f
c d e f
but I want to have an output like this
col1 col2 col3 col4 col5 col6
a b c d e f
b c e f
c d e f

Answer 1

Table and data def shamelessly stolen from #xehpuk
CREATE TABLE split_column (
id integer PRIMARY KEY,
col text NOT NULL
)
data
INSERT INTO split_column (id, col) VALUES
(1, 'a,b,c,d,e,f'),
(2, 'b,c,e,f'),
(3, 'c,d,e,f')
Use Case statements in query:
select case when position('a' in col)::bool then 'a' end as col1,
case when position('b' in col)::bool then 'b' end as col2,
case when position('c' in col)::bool then 'c' end as col3,
case when position('d' in col)::bool then 'd' end as col4,
case when position('e' in col)::bool then 'e' end as col5,
case when position('f' in col)::bool then 'f' end as col6
from aaa.split_column
col1
col2
col3
col4
col5
col6
a
b
c
d
e
f
null
b
c
null
e
f
null
null
c
d
e
f

Answer 2

Given this table:
CREATE TABLE split_column (
id integer PRIMARY KEY,
col text NOT NULL
)
And this data:
INSERT INTO split_column (id, col) VALUES
(1, 'a,b,c,d,e,f'),
(2, 'b,c,e,f'),
(3, 'c,d,e,f')
The first row contains all values:
SELECT string_to_array(col, ',') AS values
FROM split_column
ORDER BY id
LIMIT 1
values
{a,b,c,d,e,f}
We use it to create a mapping from col1..colN to the values:
WITH complete AS (
SELECT string_to_array(col, ',') AS values
FROM split_column
ORDER BY id
LIMIT 1
)
SELECT 'col' || value.ordinality AS key, value
FROM complete, unnest(complete.values) WITH ORDINALITY AS value
key
value
col1
a
col2
b
col3
c
col4
d
col5
e
col6
f
We aggregate the rows to JSON objects:
WITH complete AS (
SELECT string_to_array(col, ',') AS values
FROM split_column
ORDER BY id
LIMIT 1
), map AS (
SELECT 'col' || value.ordinality AS key, value
FROM complete, unnest(complete.values) WITH ORDINALITY AS value
)
SELECT id, jsonb_object_agg(map.key, map.value) AS object
FROM split_column, string_to_table(col, ',') AS col
JOIN map
ON col = map.value
GROUP BY id
ORDER BY id
id
object
1
{"col1": "a", "col2": "b", "col3": "c", "col4": "d", "col5": "e", "col6": "f"}
2
{"col2": "b", "col3": "c", "col5": "e", "col6": "f"}
3
{"col3": "c", "col4": "d", "col5": "e", "col6": "f"}
And then we "destructure" them back into records:
WITH complete AS (
SELECT string_to_array(col, ',') AS values
FROM split_column
ORDER BY id
LIMIT 1
), map AS (
SELECT 'col' || value.ordinality AS key, value
FROM complete, unnest(complete.values) WITH ORDINALITY AS value
), agg AS (
SELECT id, jsonb_object_agg(map.key, map.value) AS object
FROM split_column, string_to_table(col, ',') AS col
JOIN map
ON col = map.value
GROUP BY id
)
SELECT agg.id, cols.*
FROM agg, jsonb_to_record(agg.object) AS cols(col1 text, col2 text, col3 text, col4 text, col5 text, col6 text)
ORDER BY id
id
col1
col2
col3
col4
col5
col6
1
a
b
c
d
e
f
2
b
c
e
f
3
c
d
e
f
db<>fiddle