Mysql AVG()函数实例 使用AVG()函数求平均价格

mysql> CREATE TABLE IF NOT EXISTS multimeters
    -> (
    ->   id             INT             AUTO_INCREMENT PRIMARY KEY,
    ->   model          CHAR(10)        NOT NULL,
    ->   price          DECIMAL(3,2)    NOT NULL
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO multimeters (model, price)   VALUES ("Standard", 11.75);
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> INSERT INTO multimeters (model, price)   VALUES ("Super", 19.50);
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> INSERT INTO multimeters (model, price)   VALUES ("DeLuxe", 24.99);
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> SELECT * FROM multimeters;
+----+----------+-------+
| id | model    | price |
+----+----------+-------+
|  1 | Standard |  9.99 |
|  2 | Super    |  9.99 |
|  3 | DeLuxe   |  9.99 |
+----+----------+-------+
3 rows in set (0.00 sec)

mysql> SELECT AVG(price) AS avg_price --//AVG()函数 求平均价格
    -> FROM multimeters;
+-----------+
| avg_price |
+-----------+
|  9.990000 |
+-----------+
1 row in set (0.00 sec)

mysql> # delete this sample table
mysql> DROP TABLE IF EXISTS multimeters;
Query OK, 0 rows affected (0.00 sec)