Tuesday, December 21, 2010

Custom Sort Order on Postgresql

Given the countries database, how to place US on top of the list?

Click to expand countries database:
create table countries
(
country text not null unique
);

create index on countries(country);


insert into countries values
('Afghanistan'),
('Albania'),
('Algeria'),
('American Samoa'),
('Andorra'),
('Angola'),
('Anguilla'),
('Antarctica'),
('Antigua and Barbuda'),
('Argentina'),
('Armenia'),
('Aruba'),
('Australia'),
('Austria'),
('Azerbaijan'),
('Bahamas'),
('Bahrain'),
('Bangladesh'),
('Barbados'),
('Belarus'),
('Belgium'),
('Belize'),
('Benin'),
('Bermuda'),
('Bhutan'),
('Bolivia'),
('Bosnia and Herzegovina'),
('Botswana'),
('Bouvet Island'),
('Brazil'),
('British Indian Ocean Territory'),
('Brunei Darussalam'),
('Bulgaria'),
('Burkina Faso'),
('Burundi'),
('Cambodia'),
('Cameroon'),
('Canada'),
('Cape Verde'),
('Cayman Islands'),
('Central African Republic'),
('Chad'),
('Chile'),
('China'),
('Christmas Island'),
('Cocos (Keeling) Islands'),
('Colombia'),
('Comoros'),
('Congo'),
('Congo, The Democratic Republic of The'),
('Cook Islands'),
('Costa Rica'),
('Cote D''ivoire'),
('Croatia'),
('Cuba'),
('Cyprus'),
('Czech Republic'),
('Denmark'),
('Djibouti'),
('Dominica'),
('Dominican Republic'),
('Easter Island'),
('Ecuador'),
('Egypt'),
('El Salvador'),
('Equatorial Guinea'),
('Eritrea'),
('Estonia'),
('Ethiopia'),
('Falkland Islands (Malvinas)'),
('Faroe Islands'),
('Fiji'),
('Finland'),
('France'),
('French Guiana'),
('French Polynesia'),
('French Southern Territories'),
('Gabon'),
('Gambia'),
('Georgia'),
('Germany'),
('Ghana'),
('Gibraltar'),
('Greece'),
('Greenland'),
('Grenada'),
('Guadeloupe'),
('Guam'),
('Guatemala'),
('Guinea'),
('Guinea-bissau'),
('Guyana'),
('Haiti'),
('Heard Island and Mcdonald Islands'),
('Honduras'),
('Hong Kong'),
('Hungary'),
('Iceland'),
('India'),
('Indonesia'),
('Iran'),
('Iraq'),
('Ireland'),
('Israel'),
('Italy'),
('Jamaica'),
('Japan'),
('Jordan'),
('Kazakhstan'),
('Kenya'),
('Kiribati'),
('Korea, North'),
('Kosovo'),
('Kuwait'),
('Kyrgyzstan'),
('Laos'),
('Latvia'),
('Lebanon'),
('Lesotho'),
('Liberia'),
('Libyan Arab Jamahiriya'),
('Liechtenstein'),
('Lithuania'),
('Luxembourg'),
('Macau'),
('Macedonia'),
('Madagascar'),
('Malawi'),
('Malaysia'),
('Maldives'),
('Mali'),
('Malta'),
('Marshall Islands'),
('Martinique'),
('Mauritania'),
('Mauritius'),
('Mayotte'),
('Mexico'),
('Micronesia, Federated States of'),
('Moldova, Republic of'),
('Monaco'),
('Mongolia'),
('Montenegro'),
('Montserrat'),
('Morocco'),
('Mozambique'),
('Myanmar'),
('Namibia'),
('Nauru'),
('Nepal'),
('Netherlands'),
('Netherlands Antilles'),
('New Caledonia'),
('New Zealand'),
('Nicaragua'),
('Niger'),
('Nigeria'),
('Niue'),
('Norfolk Island'),
('Northern Mariana Islands'),
('Norway'),
('Oman'),
('Pakistan'),
('Palau'),
('Palestinian Territory'),
('Panama'),
('Papua New Guinea'),
('Paraguay'),
('Peru'),
('Philippines'),
('Pitcairn'),
('Poland'),
('Portugal'),
('Puerto Rico'),
('Qatar'),
('Reunion'),
('Romania'),
('Russia'),
('Rwanda'),
('Saint Helena'),
('Saint Kitts and Nevis'),
('Saint Lucia'),
('Saint Pierre and Miquelon'),
('Saint Vincent and The Grenadines'),
('Samoa'),
('San Marino'),
('Sao Tome and Principe'),
('Saudi Arabia'),
('Senegal'),
('Serbia and Montenegro'),
('Seychelles'),
('Sierra Leone'),
('Singapore'),
('Slovakia'),
('Slovenia'),
('Solomon Islands'),
('Somalia'),
('South Africa'),
('South Georgia and The South Sandwich Islands'),
('Spain'),
('Sri Lanka'),
('Sudan'),
('Suriname'),
('Svalbard and Jan Mayen'),
('Swaziland'),
('Sweden'),
('Switzerland'),
('Syria'),
('Taiwan'),
('Tajikistan'),
('Tanzania, United Republic of'),
('Thailand'),
('Timor-leste'),
('Togo'),
('Tokelau'),
('Tonga'),
('Trinidad and Tobago'),
('Tunisia'),
('Turkey'),
('Turkmenistan'),
('Turks and Caicos Islands'),
('Tuvalu'),
('Uganda'),
('Ukraine'),
('United Arab Emirates'),
('United Kingdom'),
('United States'),
('United States Minor Outlying Islands'),
('Uruguay'),
('Uzbekistan'),
('Vanuatu'),
('Vatican City'),
('Venezuela'),
('Vietnam'),
('Virgin Islands, British'),
('Virgin Islands, U.S.'),
('Wallis and Futuna'),
('Western Sahara'),
('Yemen'),
('Zambia'),
('Zimbabwe');


In Postgres, false sorts first, true sorts last

select n from (values(true),(false)) as x(n) order by n

n 
---
 f
 t
(2 rows)

So here's how to sort non-US last (which essentially sorts US first):

select country from countries order by country <> 'United States', country


If you want to use it on other RDBMS, use CASE WHEN yourConditionHere and use integer:

select country from countries 
order by 

 case when country = 'United States' then 1 else 2 end
 
 ,country


If you want to sort two countries first, use CASE yourFieldNameHere:

select country from countries 
order by 
 case country 
 when 'United States' then 1 
 when 'Philippines' then 2
 else 3 
 end
 
 ,country




Keyword search: Postgres sort order custom

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