Vertica UNION and ORDER BY

Question

I want to use ORDER BY clause but still have one specific entry on the top. I thought this might do it but Vertica is ignoring the ORDER BY clause on the second query:

(SELECT country_id, country_name 
FROM country_dim 
WHERE country_dim.iso_country_code LIKE 'US')
UNION 
(SELECT country_id, country_name 
FROM country_dim 
WHERE country_dim.iso_country_code NOT LIKE 'US' 
ORDER BY country_name ASC)

Resulting in

12  United States of America
10  Germany
5   Brazil
6   Canada
7   China
8   France
4   Algeria
3   Aland Islands
2   Albania
8   Denmark
11  United Arab Emirates
13  Central African Republic
-1  Unknown
14  Svalbard and Jan Mayen

DDL is

CREATE TABLE country_dim
(
    country_id int NOT NULL,
    iso_country_code char(2) NOT NULL,
    country_name varchar(512) NOT NULL,
    create_ts timestamptz,
    update_ts timestamptz
);

ALTER TABLE country_dim ADD CONSTRAINT country_dim_pk PRIMARY KEY (country_id) DISABLED;

Answer 1

The query needs ORDER BY in the end, not in the subqueries (and note that the parentheses are optional there, at least in standard SQL, not sure if Vertica requires them):

( SELECT country_id, country_name 
  FROM country_dim 
  WHERE iso_country_code LIKE 'US')
UNION 
( SELECT country_id, country_name 
  FROM country_dim 
  WHERE iso_country_code NOT LIKE 'US')     -- without ORDER BY
ORDER BY 
    CASE WHEN iso_country_code LIKE 'US' THEN 0 ELSE 1 END ASC,
    country_name ASC ; 

But since you are grabbing all the data from the same table, there is no need for the UNION and the subqueries:

SELECT country_id, country_name 
FROM country_dim 
ORDER BY 
    CASE WHEN iso_country_code LIKE 'US' THEN 0 ELSE 1 END ASC,
    country_name ASC ;