MySQL中 LEFT JOIN 做环比查询时报错,单独运行括号内代码,可以正常查询到数据

Question

单独运行括号内代码,可以正常查询到数据

SELECT 名称,sum(已付金额) as 202109销售额 FROM `order`
where YEAR(订单日期) ='2021' and MONTH(订单日期)='09'
GROUP BY 名称;

使用左链接后报错

(
SELECT 名称,sum(已付金额) as 202109销售额 FROM `order`
where YEAR(订单日期) ='2021' and MONTH(订单日期)='09'
GROUP BY 名称) as a

left join(
SELECT 名称,sum(已付金额) as 202009销售额 FROM `order`
where YEAR(订单日期) ='2020' and MONTH(订单日期)='09'
GROUP BY 名称)as b  on a.名称 = b.名称;

报错内容:
(
SELECT 名称,sum(已付金额) as 202109销售额 FROM order
where YEAR(订单日期) ='2021' and MONTH(订单日期)='09'
GROUP BY 名称) as a

left join(
SELECT 名称,sum(已付金额) as 202009销售额 FROM order
where YEAR(订单日期) ='2020' and MONTH(订单日期)='09'
GROUP BY 名称)as b on a.名称 = b.名称

1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'as a

left join(
SELECT 名称,sum(已付金额) as 202009销售额 FROM `ord' at line 4

时间: 0s

在线等答案

Answer 1

开头要加上select * from ,如下

select * from
(
SELECT 名称,sum(已付金额) as 202109销售额 FROM order
where YEAR(订单日期) ='2021' and MONTH(订单日期)='09'
GROUP BY 名称) as a
left join(
SELECT 名称,sum(已付金额) as 202009销售额 FROM order
where YEAR(订单日期) ='2020' and MONTH(订单日期)='09'
GROUP BY 名称)as b on a.名称 = b.名称;