带IN子句的MySQL子查询

Question

This query works fine:

SELECT country_name FROM countries WHERE country_id IN (23,86,79)

so I can get the list of countries' name based on those country_id. But what I want is to get them with a subquery like:

SELECT country_name  FROM countries WHERE country_id IN (SELECT office_id FROM countries WHERE country_code='FRA')

I can get the first name of the office Id and not all (in this case should be 4). The office_id and country_id are Int. Any helps?

Answer 1

why do you need such wrong/long turn query. your posted query (below) with subquery

SELECT country_name 
FROM countries 
WHERE country_id IN ( SELECT office_id 
                      FROM countries 
                      WHERE country_code='FRA' )

Can be simpliy

SELECT country_name 
FROM countries 
WHERE country_code='FRA';