双数据MySQL JOIN

时间：2018-10-02 18:18:42

标签： mysql join

我在MySQL中具有三个表结构，如下所示：

+-----------------------+
| Tables_in_resort_wear |
+-----------------------+
| Category              |
| Categorysub           |
| Items                 |
+-----------------------+
  1. 表类别：
+-------------+------------------+---------------+
| ID_Category | Name_Category    | Rank_Category |
+-------------+------------------+---------------+
|         101 | resort wear bali |             1 |
|         102 | bali clothing    |             1 |
|         103 | plus size resort |             3 |
|         104 | bali wholesale   |             4 |
|         105 | bali dress       |             5 |
|         106 | bali caftan      |             6 |
+-------------+------------------+---------------+
  1. 表类别子
+----------------+-------------+------------------------+------------------+
| ID_Categorysub | ID_Category | Name_Categorysub       | Rank_Categorysub |
+----------------+-------------+------------------------+------------------+
|            630 |         103 | plus size resortwear1  |                1 |
|            625 |         101 | resort wear bali 1     |                1 |
|            626 |         101 | resort wear bali 2     |                2 |
|            627 |         102 | bali clothing 1        |                1 |
|            628 |         102 | bali clothing 2        |                2 |
|            629 |         103 | plus size resortwear2  |                2 |
|            631 |         104 | bali wholesale1        |                1 |
|            632 |         104 | bali wholesale2        |                2 |
|            633 |         105 | bali dress 1           |                1 |
|            634 |         105 | bali dress 2           |                2 |
|            635 |         106 | bali caftan 1          |                1 |
|            636 |         106 | balicaftan 2           |                2 |
+----------------+-------------+------------------------+------------------+
  1. 表项
+----------+-------------+----------------+----------------------+----------------------------------------+
| ID_Items | ID_Category | ID_Categorysub | Code_Items           | Name_Items                             |
+----------+-------------+----------------+----------------------+----------------------------------------+
|     2519 |         101 |            625 | jm4828 long kaftan   | long kaftan resort wear dress          |
|     2520 |         101 |            625 | jm4828 long kaftan   | juwita moon long kaftan                |
|     2521 |         101 |            625 | jm4828 long dress    | jm4828 long tropical resort wear dress |
|     2522 |         101 |            625 | jm4828 resort wear   | jm4828 juwita moon bali tropical dress |
|     2523 |         101 |            626 | jm4828 long kaftan   | jm4828 long kaftan dress bali          |
|     2524 |         101 |            626 | jm4828 kaftan bali   | jm4828 women kaftan bali design        |
|     2525 |         101 |            626 | jm4828 bali kaftan   | jm4828 juwita moon bali kaftan design  |
|     2526 |         101 |            626 | jm4828 bali resortwe | jm4828 bali resort wear long dress     |
|     2527 |         102 |            627 | jm44dm bali women    | jm44dm bali resort wear long dress     |
|     2528 |         102 |            627 | jm44dm bali women    | jm44dm resort wear dress bali          |
|     2529 |         102 |            627 | jm44dm bali dress    | jm44dm bali long dress design          |
|     2530 |         102 |            627 | jm44dm bali dress    | jm44dm women bali dress                |
|     2531 |         102 |            628 | jm44dm bali dress    | jm44dm women long dress bali design    |
|     2532 |         102 |            628 | jm44dm bali longdres | jm44dm bali long dress design          |
|     2533 |         102 |            628 | jm44dm resort wear   | jm44dm resort wear long dress          |
|     2534 |         102 |            628 | jm44dm bali caftan   | jm44dm bali caftan                     |
|     2535 |         103 |            630 | jm18 plus size bali  | juwitamoon women plus size             |
|     2536 |         103 |            630 | jm18 plus size bali  | juwita moon women plus sizes bali      |
|     2537 |         103 |            630 | jm7002 bali plus siz | women plus size resort wear bali       |
|     2538 |         103 |            630 | jm7002 plus size bal | best plus size caftan bali             |
|     2539 |         103 |            629 | jm1333 bali plus siz | juwita moon bali plus size shirt dress |
|     2540 |         103 |            629 | jm44dm plus size     | juwita moon plus size long dress       |
|     2541 |         103 |            629 | jm18 plus size bali  | made in bali women plus size caftan    |
|     2542 |         103 |            629 | jm7002 plus size bal | juwita moon plus size women caftan     |
+----------+-------------+----------------+----------------------+----------------------------------------+

我想显示这3个表中的一些数据，为此我使用了JOIN。

这是我的查询

SELECT items.id_items, 
       items.name_items, 
       category.name_category, 
       categorysub.id_categorysub, 
       categorysub.name_categorysub 
FROM   category 
       JOIN items 
         ON category.id_category = items.id_category 
       JOIN categorysub 
         ON category.id_category = categorysub.id_category 
LIMIT  8

但是，结果在ID_Items中显示了一个双精度数据，如下所示：

+----------+----------------------------------------+------------------+----------------+--------------------+
| ID_Items | Name_Items                             | Name_Category    | ID_Categorysub | Name_Categorysub   |
+----------+----------------------------------------+------------------+----------------+--------------------+
|     2519 | long kaftan resort wear dress          | resort wear bali |            625 | resort wear bali 1 |
|     2519 | long kaftan resort wear dress          | resort wear bali |            626 | resort wear bali 2 |
|     2520 | juwita moon long kaftan                | resort wear bali |            625 | resort wear bali 1 |
|     2520 | juwita moon long kaftan                | resort wear bali |            626 | resort wear bali 2 |
|     2521 | jm4828 long tropical resort wear dress | resort wear bali |            625 | resort wear bali 1 |
|     2521 | jm4828 long tropical resort wear dress | resort wear bali |            626 | resort wear bali 2 |
|     2522 | jm4828 juwita moon bali tropical dress | resort wear bali |            625 | resort wear bali 1 |
|     2522 | jm4828 juwita moon bali tropical dress | resort wear bali |            626 | resort wear bali 2 |
+----------+----------------------------------------+------------------+----------------+--------------------+

我想显示一些类似的数据，但ID_Items中不包含重复数据。我已经尝试使用DISTINCT，并且得到了与上述相同的数据。 我该如何选择最好的方法？

2 个答案:

答案 0 :(得分：0)

尝试使用分组依据

SELECT items.id_items, 
       items.name_items, 
       category.name_category, 
       categorysub.id_categorysub, 
       categorysub.name_categorysub 
FROM   category 
       JOIN items 
         ON category.id_category = items.id_category 
       JOIN categorysub 
         ON category.id_category = categorysub.id_category 
GROUP  BY id_items

答案 1 :(得分：0)

首先您加入category和categorysub，然后可以同时加入items。

SELECT items.id_items, 
       items.name_items, 
       category.name_category, 
       categorysub.id_categorysub, 
       categorysub.name_categorysub 
FROM   category 
       JOIN categorysub 
         ON category.id_category = categorysub.id_category 
       JOIN items 
         ON category.id_category = items.id_category 
        AND categorysub.ID_Categorysub = items.ID_Categorysub 
LIMIT  8

但这是针对您具有复合主键的情况。

对于您的数据，我认为ID_Categorysub是唯一的，因此实际上您只需要：

       JOIN items 
         ON categorysub.ID_Categorysub = items.ID_Categorysub
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