我有兩個一對多關係表。我想檢查映射表中是否有任何重複條目。MySQL檢查一對多關係中的重複條目
客戶:
+----------------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------------------+--------------+------+-----+---------+----------------+
| uid | int(11) | NO | PRI | | auto_increment |
| active | tinyint(1) | NO | | | |
| locked | tinyint(1) | NO | | | |
+----------------------------+--------------+------+-----+---------+----------------+
items_mapping:
+--------------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+---------------+------+-----+---------+----------------+
| uid | int(11) | NO | PRI | | auto_increment |
| customer_uid | int(11) | NO | | | |
| device_uid | int(11) | NO | | | |
| offered | float(11,2) | NO | | | |
+--------------+---------------+------+-----+---------+----------------+
如何檢查是否有任何客戶,在表的表items_mapping,誰擁有複製device_uid?
總之,這將工作:
+-------+--------------+------------+---------+
| uid | customer_uid | device_uid | offered |
+-------+--------------+------------+---------+
| 1132 | 53442 | 24 | 2.00 |
| 8242 | 53442 | 45 | 4.00 |
| 15122 | 53442 | 12 | 5.00 |
+-------+--------------+------------+---------+
但它不應該是:
+-------+--------------+------------+---------+
| uid | customer_uid | device_uid | offered |
+-------+--------------+------------+---------+
| 1132 | 53442 | 24 | 2.00 |
| 8242 | 53442 | 45 | 4.00 |
| 15122 | 53442 | 24 | 2.00 |
+-------+--------------+------------+---------+
是有可能的兩個不同的客戶(customer_uid)擁有同一個設備(device_uid)? – mitkosoft
是的,許多客戶可以從同一個設備獲得相同的報價,但是他們不能爲一個客戶提供相同的報價。 – ln9187