我有以下关系模式:
Country(code: Str, name: Str, capital: Str, area: int)
code (this is the usual country code, e.g. CDN for Canada, F for France, I for Italy)
name (the country name) capital (the capital city, e.g. Rome for Italy)
area (The mass land the country occupies in square Km)
Economy (country: Str, GDP: int, inflation: int, military: int, poverty: int)
country is FK to the Country table
GDP (gross domestic product)
inflation (annual inflation rate)
military (military spending as percentage of the GDP)
poverty rate (percentage of population below the poverty line)
Language (country: Str, language: Str, percentage: int)
country is FK to the Country table
language is a spoken language name
percentage (percentage of population speaking the language)
我需要编写一个查询,查找使用语言最多的国家/地区的贫困率。
我编写了以下查询:
SELECT poverty
FROM(
SELECT COUNT(language) as langnum, country
FROM "Language"
GROUP BY country) AS conto
JOIN "Economy" AS E
ON E.country=conto.country
ORDER BY conto.langnum DESC
LIMIT 1
如果只有一个国家拥有最多的语言,那么这个方法显然是有效的,但如果有多个国家都拥有最多的语言,我该怎么办呢?