Convert singapore postcodes to districts

districts.sql

create or replace function singapore_postcode_to_district (code text, out district_num int, out district_name text)
as $$
begin
	case substring(code from 1 for 2)::int
	when 01, 02, 03, 04, 05, 06 then
		district_num := 1;
		district_name := 'Raffles Place, Cecil, Marina, People''s Park';
	when 07, 08 then
		district_num := 2;
		district_name := 'Anson, Tanjong Pagar';
	when 14,15, 16 then
		district_num := 3;
		district_name := 'Queenstown, Tiong Bahru';
	when 09, 10 then
		district_num := 4;
		district_name := 'Telok Blangah, Harbourfront';
	when 11, 12, 13 then
		district_num := 5;
		district_name := 'Pasir Panjang, Hong Leong Garden, Clementi New Town';
	when 17 then
		district_num := 6;
		district_name := 'High Street, Beach Road (part)';
	when 18, 19 then
		district_num := 7;
		district_name := 'Middle Road, Golden Mile';
	when 20, 21 then
		district_num := 8;
		district_name := 'Little India';
	when 22, 23 then
		district_num := 9;
		district_name := 'Orchard, Cairnhill, River Valley';
	when 24, 25, 26, 27 then
		district_num := 10;
		district_name := 'Ardmore, Bukit Timah, Holland Road, Tanglin';
	when 28, 29, 30 then
		district_num := 11;
		district_name := 'Watten Estate, Novena, Thomson';
	when 31, 32, 33 then
		district_num := 12;
		district_name := 'Balestier, Toa Payoh, Serangoon';
	when 34, 35, 36, 37 then
		district_num := 13;
		district_name := 'Macpherson, Braddell';
	when 38, 39, 40, 41 then
		district_num := 14;
		district_name := 'Geylang, Eunos';
	when 42, 43, 44, 45 then
		district_num := 15;
		district_name := 'Katong, Joo Chiat, Amber Road';
	when 46, 47, 48 then
		district_num := 16;
		district_name := 'Bedok, Upper East Coast, Eastwood, Kew Drive';
	when 49, 50, 81 then
		district_num := 17;
		district_name := 'Loyang, Changi';
	when 51, 52 then
		district_num := 18;
		district_name := 'Tampines, Pasir Ris';
	when 53, 54, 55, 82 then
		district_num := 19;
		district_name := 'Serangoon Garden, Hougang, Ponggol';
	when 56, 57 then
		district_num := 20;
		district_name := 'Bishan, Ang Mo Kio';
	when 58, 59 then
		district_num := 21;
		district_name := 'Upper Bukit Timah, Clementi Park, Ulu Pandan';
	when 60, 61, 62, 63, 64 then
		district_num := 22;
		district_name := 'Jurong';
	when 65, 66, 67, 68 then
		district_num := 23;
		district_name := 'Hillview, Dairy Farm, Bukit Panjang, Choa Chu Kang';
	when 69, 70, 71 then
		district_num := 24;
		district_name := 'Lim Chu Kang, Tengah';
	when 72, 73 then
		district_num := 25;
		district_name := 'Kranji, Woodgrove';
	when 77, 78 then
		district_num := 26;
		district_name := 'Upper Thomson, Springleaf';
	when 75, 76 then
		district_num := 27;
		district_name := 'Yishun, Sembawang';
	when 79, 80 then
		district_num := 28;
		district_name := 'Seletar';
	else
	end case;
end;
$$ language plpgsql;