MySQL计算多个SUM变量

问题描述

我想计算2 sum（）我尝试过查询，如下所示，但它运行很慢。有什么更好的想法吗？

SELECT customer,SUM(CASE WHEN book_day BETWEEN '2020-01-01' AND '2020-01-31'  
                THEN pax+free 
                ELSE 0 
                END) AS January,SUM(CASE WHEN book_day BETWEEN '2020-02-01' AND '2020-02-31'  
                THEN pax+free 
                ELSE 0 
                END) AS February,( SUM(CASE WHEN book_day BETWEEN '2020-01-01' AND '2020-01-31'  
                  THEN pax+free 
                  ELSE 0 
                  END) + 
         SUM(CASE WHEN book_day BETWEEN '2020-02-01' AND '2020-02-31'  
                  THEN pax+free 
                  ELSE 0 
                  END) ) AS total
 FROM rezervations  

我如何使像January + February as total这样的简单

解决方法

将BETWEEN '2020-01-01' AND '2020-02-29'保留在where子句中。

确保book_day列上有索引

SELECT customer,SUM(CASE WHEN book_day BETWEEN '2020-01-01' AND '2020-01-31' THEN pax+free ELSE 0 END) as January,SUM(CASE WHEN book_day BETWEEN '2020-02-01' AND '2020-02-29'  THEN pax+free ELSE 0 END) as February,(SUM(CASE WHEN book_day BETWEEN '2020-01-01' AND '2020-02-29'  THEN pax+free ELSE 0 END) ) as total
 FROM rezervations 
WHERE
book_day BETWEEN '2020-01-01' AND '2020-02-29'