How to multiply columns and then sum the rows with similar records like customer name?

To understand this, let us create a table with fields like ID, Customer Name, Items, Price. We will first multiply the items with price. After that the rows with similar records i.e. same customer name will get added.

Let us first create a table:

mysql> create table DemoTable
(
   CustomerId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   CustomerName varchar(100),
   CustomerItems int,
   CustomerPrice int
);
Query OK, 0 rows affected (0.54 sec)

Following is the query to insert some records in the table using insert command:

mysql> insert into DemoTable(CustomerName,CustomerItems,CustomerPrice)values('Larry',3,450);
Query OK, 1 row affected (0.24 sec)
mysql> insert into DemoTable(CustomerName,CustomerItems,CustomerPrice)values('Mike',2,550);
Query OK, 1 row affected (0.42 sec)
mysql> insert into DemoTable(CustomerName,CustomerItems,CustomerPrice)values('Larry',4,1000);
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable(CustomerName,CustomerItems,CustomerPrice)values('Larry',1,100);
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable(CustomerName,CustomerItems,CustomerPrice)values('Mike',5,200);
Query OK, 1 row affected (0.71 sec)

Following is the query to display records from the table using select command:

mysql> select *from DemoTable;

This will produce the following output

+------------+--------------+---------------+---------------+
| CustomerId | CustomerName | CustomerItems | CustomerPrice |
+------------+--------------+---------------+---------------+
|          1 | Larry        |             3 |           450 |
|          2 | Mike         |             2 |           550 |
|          3 | Larry        |             4 |          1000 |
|          4 | Larry        |             1 |           100 |
|          5 | Mike         |             5 |           200 |
+------------+--------------+---------------+---------------+
5 rows in set (0.00 sec)

Here is the query to multiply columns (Items * Price) and then sum rows with similar record:

mysql> SELECT CustomerName, SUM( CustomerItems* CustomerPrice) AS TOTAL_PRICE FROM DemoTable
GROUP BY CustomerName;

This will produce the following output

+--------------+-------------+
| CustomerName | TOTAL_PRICE |
+--------------+-------------+
| Larry        | 5450        |
| Mike         | 2100        |
+--------------+-------------+
2 rows in set (0.05 sec)