MySQL - Hur filtrerar man och visar maxvärde från en grupp?

En möjlig lösning är att använda HAVING och ALL

SELECT s.shopname AS "Store",
   e.empname AS "Employee",
   e1.empname AS "Manager",
   SUM(p.amount) AS "Total Sales"
FROM fss_Shop s
   JOIN fss_Employee e ON e.shopid = s.shopid
   JOIN fss_Payment p ON p.empnin = e.empnin
   JOIN fss_Employee e1 ON e1.empnin = e.mgrnin
GROUP BY e.empname, s.shopid
HAVING SUM(p.amount) >= ALL(
   SELECT SUM(p.amount)
   FROM fss_Employee e
   JOIN fss_Payment p ON p.empnin = e.empnin
   WHERE e.shopid = s.shopid
   GROUP BY e.empname
)

om ALL fungerar inte för dig. Du kan ändra det så här

SELECT s.shopname AS "Store",
   e.empname AS "Employee",
   e1.empname AS "Manager",
   SUM(p.amount) AS "Total Sales"
FROM fss_Shop s
   JOIN fss_Employee e ON e.shopid = s.shopid
   JOIN fss_Payment p ON p.empnin = e.empnin
   JOIN fss_Employee e1 ON e1.empnin = e.mgrnin
GROUP BY e.empname, e.shopid
HAVING SUM(p.amount) = (
   SELECT MAX(t.samount)
   FROM
   (
     SELECT SUM(p.amount) samount
     FROM fss_Employee emp
     JOIN fss_Payment p ON p.empnin = emp.empnin
     WHERE emp.shopid = e.shopid
     GROUP BY emp.empname
   ) t
)

ok och nästa version som undviker korrelerad underfråga bakom FROM

SELECT s.shopname AS "Store",
   e.empname AS "Employee",
   e1.empname AS "Manager",
   SUM(p.amount) AS "Total Sales"
FROM fss_Shop s
   JOIN fss_Employee e ON e.shopid = s.shopid
   JOIN fss_Payment p ON p.empnin = e.empnin
   JOIN fss_Employee e1 ON e1.empnin = e.mgrnin
GROUP BY e.empnin, e.shopid
HAVING (e.shopid, SUM(p.amount)) IN
(
  SELECT t.shopid, MAX(t.samount)
  FROM 
  (
     SELECT emp.shopid, SUM(p.amount) samount
     FROM fss_Employee emp
     JOIN fss_Payment p ON p.empnin = emp.empnin
     GROUP BY emp.empname, emp.shopid
  ) t
  GROUP BY t.shopid
)