PostgreSQL Substring pattern with spaces - sql

Question

I've been struggling with this query trying solutions found in this forum, but I can't go on. I need help.
I have a column that stores ship names througout the ship's life and I want to split them into three columns.
Mainly I have these three options,
a) Only one name
select t2.esp1,t2.espectro,t2.espectro1, t2.id from(
select substring(t.espectro, t.posfin)::varchar as esp1, t.espectro,t.espectro1,t.id from(
select "Id" as id, strpos(shipname, ', ') as posinic, strpos(shipname, ' y ') as posfin,shipname as espectro, shipname1 as espectro1 from ships) t)t2 (esp1, espectro, espectro1, id)
where t2.esp1 not like '% y %'`)
b) two names
select t2.esp1,t2.espectro,t2.espectro1, t2.id from(
select substring(t.espectro,1, t.posfin)::varchar as esp1, t.espectro,t.espectro1,t.id from(
select "Id" as id, strpos(shipname, ', ') as posinic, strpos(shipname ' y ') as posfin,shipname as espectro, shipname1 as espectro1 from ships) t)t2 (esp1, espectro, espectro1, id)
where t2.esp1 not like '%, %'`) and for the second name (`select t2.esp1,t2.espectro,t2.espectro1, t2.id from(
select substring(t.espectro, t.posfin)::varchar as esp2, t.espectro,t.espectro2,t.id from(
select "Id" as id, strpos(shipname, ', ') as posinic, strpos(shipname, ' y ') as posfin,shipname as espectro, shipname2 as espectro2 from ships) t)t2 (esp2, espectro, espectro2, id)
where t2.esp2 like '% y %' and t2.espectro not like '%, %';
and c) three names: I could get first
select substring(t.espectro,1,t.posicion) from(
select strpos(shipname, ',') as posicion,shipname as espectro from ships) t;` and third `select t2.esp3,t2.espectro,t2.espectro3, t2.id from(
select substring(t.espectro, t.posfin)::varchar as esp3, t.espectro,t.espectro3,t.id from(
select "Id" as id, strpos(shipname, ', ') as posinic, strpos(shipname, ' y ') as posfin,shipname as espectro, shipname3 as espectro3 from ships) t)t2 (esp3, espectro, espectro3, id)
where t2.esp3 like '% y %' and t2.espectro like '%, %';
but not second
The three named records look like this:
Nuestra Señora del Rosario, Santo Domingo y San José
I have tried this option:
select substring(t.shipsnames from '%#",_y#"%' for '#') as name2 from ships t
With several changes in the #"pattern#" to find the white spaces and get the second name.
Then I tried this option:
select t2.name2[6:7] from (regexp_split_to_array(t.shipnames, E'\\s+') as name2 from ships t) t2
But It doesn't work because not every record has the same length so some are solved like {"Santo","Domingo"} but other not like {"Rosario",","}.
I am not familiarized with regex sintax, I have found this example in the PostgreSQL documentation. Any hint?

Answer 1

When names should be split whenever they are separated by comma plus optional whitespace or with an y surrounded by mandatory whitespace the following regular expression will work:
\s*,\s*|\s+y\s+
\s: whitespace character, +: at least one, *: zero or more and | means alternation.
Example SQL utilizing this regular expression:
SELECT Id, ShipNamesArray[1] ShipName1, ShipNamesArray[2] ShipName2, ShipNamesArray[3] ShipName3
FROM (
SELECT Id, regexp_split_to_array(Shipnames, '\s*,\s*|\s+y\s+') ShipNamesArray
FROM (VALUES
(1, 'Nuestra Señora del Rosario, Santo Domingo y San José'),
(2, 'Nuestra Señora del Rosario y Santo Domingo'),
(3, 'Nuestra Señora del Rosario')
) AS ExampleShipNames (Id, ShipNames)
) AS SplitShipNames
The SQL will produce this output:
Id | ShipName1 | ShipName2 | ShipName3
-- | -------------------------- | ------------- | ---------
1 | Nuestra Señora del Rosario | Santo Domingo | San José
2 | Nuestra Señora del Rosario | Santo Domingo |
3 | Nuestra Señora del Rosario | |