Question

我正在尝试获取具有以下详细信息的销售人员列表 EmpId，推销员连续三年获得A级。

我编写了以下查询，但出现错误。

SELECT salesman, empid
FROM Sales_temp
where rating = 'A'
AND(select max(year), min(year) from Sales_temp 
 having (max(year)-min(year) = 3))
AND Count(year)=3

要过滤连续3年获得“ A”级数据，我使用了以下逻辑：

A等级的最大值（年）与A等级的最小值（年）之差= 3 计数（年）= 3。但是，出现错误：

标量子查询不能超过一列

请提出建议。

Answer 1

我想在MySQL中做到这一点的唯一方法是将您的表自我连接两次，然后由业务员进行汇总。然后，确定推销员是否至少有一项记录具有连续三个A级：

SELECT
    s1.salesman, s1.empid
FROM Sales_temp s1
INNER JOIN Sales_temp s2
    ON s1.empid = s2.empid AND s2.year = s1.year + 1
INNER JOIN Sales_temp s3
    ON s2.empid = s3.empid AND s3.year = s2.year + 1
GROUP BY
    s1.salesman, s1.empid
HAVING
    SUM(CASE WHEN s1.rating = 'A' AND s2.rating = 'A' AND s3.rating = 'A'
             THEN 1 ELSE 0 END) > 0;

Demo

中间连接表非常丑陋，但是足以说它给Sales_temp中的每条记录一个与下一年，然后是下一年配对的机会。如果可以进行三连击，并且所有三个等级均为A质量，则该推销员将出现在结果集中。

Answer 2

If you are interested in the years A was achieved

 drop table if exists sales_temp;
create table sales_temp(salesman int,empid int, rating varchar(1),year int);

insert into sales_temp values
(1,1,'a',2018),(1,1,'a',2017),(1,1,'a',2016),(1,1,'a',2015),
(2,2,'a',2018),(2,2,'a',2017),
(3,3,'b',2018),(3,3,'a',2017),(3,3,'a',2016),(3,3,'a',2015);

select salesman,empid,r1,r2,r3
from
(
select s.salesman,s.empid,year r1,
        (select year from sales_temp s1 where s1.salesman = s.salesman and s1.empid = s.empid and s1.year = s.year -1 and rating = 'a') r2,
        (select year from sales_temp s1 where s1.salesman = s.salesman and s1.empid = s.empid and s1.year = s.year -2 and rating = 'a') r3
 from sales_temp s
 where s.rating = 'a'
) s
where s.r1 is not null and s.r2 is not null and s.r3 is not null ;

+----------+-------+------+------+------+
| salesman | empid | r1   | r2   | r3   |
+----------+-------+------+------+------+
|        1 |     1 | 2018 | 2017 | 2016 |
|        1 |     1 | 2017 | 2016 | 2015 |
|        3 |     3 | 2017 | 2016 | 2015 |
+----------+-------+------+------+------+
3 rows in set (0.00 sec)

在where子句中使用group by遇到错误

2 个答案:

Demo