2つのテーブルを1つのクエリに組み合わせる

Question

私は2つのテーブルSalesとEmployeesをpostgresqlに添付しています。 私は計算する必要があります。また2015年で最も高い売り上げでトップ4人の従業員を返す クエリは、すでに会社を去ってきたemployessの売上高は、従業員番号の下にあなたの助け

フォイ事前に999 感謝しなければなりませんテスト済み

Sales

Answer 1

推奨SQL：

SELECT 
s.employee_id, emp.first_name, 
emp.last_name, s.department, 
sum(s.num_of_products) as total_product, 
sum(s.total_price) as total_price, 
s.branch_id, s.branch_city, 
s.date 
FROM sales s 
JOIN employees emp 
ON s.employee_id = emp.employee_id 
WHERE date_part('year',s.date) = '2014' 
-- '2014' is year depend on the input ex. '2015' 
GROUP BY s.employee_id, emp.first_name,emp.last_name, 
s.department, s.branch_id, s.branch_city, s.date 
-- add non aggregate function (sum,count,max,etc) field to group by if you want to show the field. 
-- not add in group by cause error 'field must appear in group by' 
ORDER BY total_product 
-- order by total_product based on total_product 
-- order by for choose order by product or price using alias 
-- order by without alias ORDER BY sum(s.num_of_products) 
-- order by will be error caused error if use num_of_products 
-- order by total_price if the TOP 4 based on total_price 
LIMIT 4; 
-- top 4 
-- top n => LIMIT n