如何在MySQL中按月分组并获得甚至连几个月都没有价值的结果

Question

我有payment数据表（MySQL）记录所有付款。我想按日期对所有付款进行分组。实际上，我想按月对他们进行分组，以分析他们在特定月份获得的收入。如果特定月份没有付款，我需要将其设置为0。

这是我的SQL代码。

SELECT SUM(p.sub_total) as sold_income , month(p.invoice_date) as income_month ,MONTHNAME(p.invoice_date) as month_name, YEAR(p.invoice_date) as income_year FROM payment p where (p.invoice_date BETWEEN '2018-01-01' AND '2018-08-01') GROUP BY DATE_FORMAT(p.invoice_date, '%Y%m')

从这段代码中，我得到以下输出：

我在“ 2018-01-01”和“ 2018-08-01”之间进行了搜索。因此应该有7个月和7个结果。如果第1个月（1月）没有付款，我想要sold_income = 0;

我该怎么做？请帮助我。...

Answer 1

生成日期并与此表格一起加入并投影结果

  SELECT SUM(p.sub_total) as sold_income , month(C_date ) as income_month ,MONTHNAME(C_date ) as month_name, YEAR(C_date ) as income_year from    

           (
                select * from 
                (select adddate('1970-01-01',t4*10000 + t3*1000 + t2*100 + t1*10 + t0) C_date from
                 (select 0 t0 union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0,
                 (select 0 t1 union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t1,
                 (select 0 t2 union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t2,
                 (select 0 t3 union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t3,
                 (select 0 t4 union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t4) v
                where C_date between '2017-08-01' and '2018-12-31'
                ) All_date
    left join  payment p on on date(p.invoice_date )=All_date.C_date
    where C_date 
    BETWEEN '2017-08-01' AND '2018-08-01'
    GROUP BY income_month ,month_name,income_year