getting an error using group by with where clause - mysql

Question

I am trying to fetch a list of salesmen with following details
EmpId, Salesman who got rating A for consecutive 3 year.
I've written the following query but getting an error.
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
To filter data of 3 consecutive years for 'A' rating I have used the following logic:
difference of max(year) for A rating minus min(year) for A rating = 3
and count(year)=3. However, I'm getting an error:
scalar sub query can't have more than one column
please suggest.

Answer 1

The only way I think of to do this in MySQL would be to self join your table twice, and then aggregate by salesman. Then, assert whether or not a salesman has at least one record with three consecutive A ratings:
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
The intermediate joined table would be quite ugly, but it suffices to say that it gives each record in Sales_temp a chance to pair up with the next year, and then the year after that. If a triplet can happen, and all three ratings are A quality, then that salesman would appear in the result set.

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)