Schema 정보만 올려주세요~

CREATE TABLE `Item` (
`index` INT(11) NOT NULL AUTO_INCREMENT,
`item_name` VARCHAR(20) NOT NULL,
PRIMARY KEY (`index`)
) ENGINE=INNODB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8 ROW_FORMAT=COMPRESSED

INSERT INTO `Item`(`index`,`item_name`)

VALUES

( NULL,'축구공'),

( NULL,'농구공'),

( NULL,'배구공'),

( NULL,'탁구공');

CREATE TABLE `Selling` (
`index` INT(11) NOT NULL AUTO_INCREMENT,
`selling_date` DATE NOT NULL,
`Item_Index` INT(11) NOT NULL,
`selling_count` INT(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`index`),
KEY `fk_Item_Index` (`Item_Index`),
CONSTRAINT `fk_Item_Index` FOREIGN KEY (`Item_Index`) REFERENCES `Item` (`index`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=INNODB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8

mysql> SELECT COUNT(DISTINCT `Item_Index`) FROM `Selling`;
+------------------------------+
| COUNT(DISTINCT `Item_Index`) |
+------------------------------+
| 2 |
+------------------------------+
1 row in set (0.00 sec)

mysql> SELECT COUNT(1), `Item`.`item_name` FROM `Selling` JOIN `Item` ON `Selling`.`Item_Index` = `Item`.`index` GROUP BY `Selling`.`Item_Index`;
+----------+-----------+
| COUNT(1) | item_name |
+----------+-----------+
| 2 | 축구공 |
| 1 | 배구공 |
+----------+-----------+
2 rows in set (0.00 sec)

Selling Table 은 데이터 무결성을 위해 폴링키를 사용했습니다~

그럼 ㅅㄱ