錯誤1140我的查詢

Question

select country.continent,round(avg(city.population),0) as c 
from city,country 
where city.countrycode = country.code; 

我已經使用這個查詢，但我得到這個錯誤

ERROR 1140（42000）位於第1行：在彙總查詢，而GROUP BY，SELECT表達＃1列表包含非聚集列'run_2sryibds0p4.country.continent';這是不符合sql_mode = only_full_group_by

請幫助我正確的解決方案和解釋請。

Answer 1

只能通過GROUP BY使用聚合AVG：

SELECT country.continent, ROUND(AVG(city.population), 0) AS c 
FROM city,country 
WHERE city.countrycode = country.code 
GROUP BY country.continent; 

更多有關GROUP BY和聚合函數（如AVG）：

• https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html
• https://dev.mysql.com/doc/refman/5.7/en/group-by-handling.html

Answer 2

SELECT country.continent,round(avg(city.population),0) as c 
FROM city.country 
WHERE city.countrycode = country.code 
GROUP BY 1 

聚合列需要按非聚合列進行分組 - 在這種情況下，應該按country.continent對人口的四捨五入平均值進行分組。

看看這裏的更多信息 https://dev.mysql.com/doc/refman/5.7/en/group-by-handling.html