สอบถามวิธี Join หลายตาราง แล้วนำมา Pivot แล้ว SUM เพื่อแสดงผลรวมของการขายแต่ละ User

# Dump of table Product_A
# ------------------------------------------------------------

DROP TABLE IF EXISTS `Product_A`;

CREATE TABLE `Product_A` (
  `DATE` date DEFAULT NULL,
  `Emp_ID` varchar(255) DEFAULT NULL,
  `Revenue` int(11) DEFAULT NULL,
  `Unit` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

LOCK TABLES `Product_A` WRITE;
/*!40000 ALTER TABLE `Product_A` DISABLE KEYS */;

INSERT INTO `Product_A` (`DATE`, `Emp_ID`, `Revenue`, `Unit`)
VALUES
	('2021-05-04','B',2500,'2\r'),
	('2021-05-04','C',1200,'1\r'),
	('2021-05-04','A',6000,'5\r'),
	('2021-05-04','E',7500,'8\r'),
	('2021-05-04','A',9250,'10\r'),
	('2021-05-04','F',11230,'1\r'),
	('2021-05-04','C',13210,'6\r'),
	('2021-05-05','D',15190,'8\r'),
	('2021-05-05','B',17170,'6\r'),
	('2021-05-05','C',19150,'12\r'),
	('2021-05-05','A',21130,'2\r'),
	('2021-05-05','E',23110,'8\r'),
	('2021-05-05','A',25090,'5\r'),
	('2021-05-05','F',27070,'8\r'),
	('2021-05-06','C',29050,'10\r'),
	('2021-05-06','D',31030,'1\r'),
	('2021-05-06','B',33010,'6\r'),
	('2021-05-06','C',34990,'8\r'),
	('2021-05-06','A',36970,'10');

/*!40000 ALTER TABLE `Product_A` ENABLE KEYS */;
UNLOCK TABLES;


# Dump of table Product_B
# ------------------------------------------------------------

DROP TABLE IF EXISTS `Product_B`;

CREATE TABLE `Product_B` (
  `DATE` date DEFAULT NULL,
  `Emp_ID` varchar(255) DEFAULT NULL,
  `Revenue` int(11) DEFAULT NULL,
  `Unit` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

LOCK TABLES `Product_B` WRITE;
/*!40000 ALTER TABLE `Product_B` DISABLE KEYS */;

INSERT INTO `Product_B` (`DATE`, `Emp_ID`, `Revenue`, `Unit`)
VALUES
	('2021-05-04','B',2500,'2\r'),
	('2021-05-04','C',1200,'1\r'),
	('2021-05-04','A',6000,'5\r'),
	('2021-05-04','E',7500,'8\r'),
	('2021-05-04','A',9250,'10\r'),
	('2021-05-04','F',11230,'1\r'),
	('2021-05-04','C',13210,'6\r'),
	('2021-05-05','B',15190,'8\r'),
	('2021-05-05','B',17170,'6\r'),
	('2021-05-05','C',19150,'12\r'),
	('2021-05-05','A',21130,'2\r'),
	('2021-05-05','E',23110,'8\r'),
	('2021-05-05','A',25090,'5\r'),
	('2021-05-05','F',27070,'8\r'),
	('2021-05-06','C',29050,'10\r'),
	('2021-05-06','B',31030,'1\r'),
	('2021-05-06','B',33010,'6\r'),
	('2021-05-06','C',34990,'8\r'),
	('2021-05-06','A',36970,'10');

/*!40000 ALTER TABLE `Product_B` ENABLE KEYS */;
UNLOCK TABLES;


# Dump of table Product_C
# ------------------------------------------------------------

DROP TABLE IF EXISTS `Product_C`;

CREATE TABLE `Product_C` (
  `DATE` date DEFAULT NULL,
  `Emp_ID` varchar(255) DEFAULT NULL,
  `Revenue` int(11) DEFAULT NULL,
  `Unit` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

LOCK TABLES `Product_C` WRITE;
/*!40000 ALTER TABLE `Product_C` DISABLE KEYS */;

INSERT INTO `Product_C` (`DATE`, `Emp_ID`, `Revenue`, `Unit`)
VALUES
	('2021-05-04','B',2500,'2\r'),
	('2021-05-04','C',1200,'1\r'),
	('2021-05-04','A',6000,'5\r'),
	('2021-05-04','E',7500,'8\r'),
	('2021-05-04','A',9250,'10\r'),
	('2021-05-04','D',11230,'1\r'),
	('2021-05-04','C',13210,'6\r'),
	('2021-05-05','B',15190,'8\r'),
	('2021-05-05','B',17170,'6\r'),
	('2021-05-05','C',19150,'12\r'),
	('2021-05-05','A',21130,'2\r'),
	('2021-05-05','E',23110,'8\r'),
	('2021-05-05','A',25090,'5\r'),
	('2021-05-05','D',27070,'8\r'),
	('2021-05-06','C',29050,'10\r'),
	('2021-05-06','B',31030,'1\r'),
	('2021-05-06','B',33010,'6\r'),
	('2021-05-06','C',34990,'8\r'),
	('2021-05-06','A',36970,'10');

/*!40000 ALTER TABLE `Product_C` ENABLE KEYS */;
UNLOCK TABLES;


# Dump of table StaffInfo
# ------------------------------------------------------------

DROP TABLE IF EXISTS `StaffInfo`;

CREATE TABLE `StaffInfo` (
  `Emp_ID` varchar(255) DEFAULT NULL,
  `Emp_Name` varchar(255) DEFAULT NULL,
  `Emp_Type` varchar(255) DEFAULT NULL,
  `Shop_code` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

LOCK TABLES `StaffInfo` WRITE;
/*!40000 ALTER TABLE `StaffInfo` DISABLE KEYS */;

INSERT INTO `StaffInfo` (`Emp_ID`, `Emp_Name`, `Emp_Type`, `Shop_code`)
VALUES
	('A','เอกราช','Sales_A','301\r'),
	('B','อภิวิชย์','Sales_A','401\r'),
	('C','อนุศร','Sales_C','201\r'),
	('D','นุเทพ','Sales_B','101\r'),
	('E','ธนากร','Sales_A','101\r'),
	('F','บรรพต','Sales_B','201');

/*!40000 ALTER TABLE `StaffInfo` ENABLE KEYS */;
UNLOCK TABLES;

SELECT
   StaffInfo.*,
   A.Product_A_REV,
   A.Product_A_UNIT,
   B.Product_B_REV,
   B.Product_B_UNIT,
   C.Product_C_REV,
   C.Product_C_UNIT 
FROM
   StaffInfo 
   LEFT JOIN
      (
         SELECT
            Emp_ID,
            SUM(Revenue) Product_A_REV,
            COUNT(Revenue) Product_A_UNIT 
         FROM
            Product_A 
         GROUP BY
            Emp_ID 
      )
      A 
      ON StaffInfo.Emp_ID = A.Emp_ID 
   LEFT JOIN
      (
         SELECT
            Emp_ID,
            SUM(Revenue) Product_B_REV,
            COUNT(Revenue) Product_B_UNIT 
         FROM
            Product_B 
         GROUP BY
            Emp_ID 
      )
      B 
      ON StaffInfo.Emp_ID = B.Emp_ID 
   LEFT JOIN
      (
         SELECT
            Emp_ID,
            SUM(Revenue) Product_C_REV,
            COUNT(Revenue) Product_C_UNIT 
         FROM
            Product_C 
         GROUP BY
            Emp_ID 
      )
      C 
      ON StaffInfo.Emp_ID = C.Emp_ID