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There is an username/password verification step first then the database has following structure

^ is primary key

* uses foreign key


1.StudentDetails table
===========================================================================  
 ID^| Username   | Password | Email       | Address * | Website |Comments
====+============+==========+=============+===========+=========+========== 
1   | xxxxxxxxxx | xxxxxxx  | xx@xxx.xxx  | 1         | http:// | text

2.Submissions table
===========================================================================================
ID^|Username*|SubmitDate|SelectedCourse*|Price*|Promotion*|SubmitComments|SubmitStatus*
===+=========+==========+===============+======+==========+==============+=================
1  |xxxxxxxxx|2013-7-12 |  int          | int  |  int     | text         | int


3.SubmitComplete table
==================================================
ID^| Username * | SelectionDate | SubmitStatus *  
====+============+===============+================
1   | xxxxxxxxxx |  2013-08-01   | int

Now I'm having an issue entering the address, when i try to enter the student details it won't accept until there is an address field, how best to tackle that? When i do an left join selecting certain fields from StudentDetails and certain fields from Addresses, addresses don't show.

Im a mysql noob, so i'd like some guidance to see if the normalising and structure has been done correctly, or could it be done better, here is the fiddle i couldn't get it to work properly, kept getting errors on the lines where i added the foreign keys, even though the building of the schema worked well on my machine.

The fiddle console says error on line 2 but it looks to me it's actually on line 76. If there's anything i was unclear on, pls let me know. Thanks

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3 回答 3

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好的，让我解释一下它会是怎样的。我用两个表格做了一个例子，你可以在下面看到。

简单模型

然后您可以创建您的查询。

mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| addresses      |
| students       |
+----------------+
2 rows in set (0.00 sec)

mysql> select * from students;
+----+----------+-----------+
| id | name     | last_name |
+----+----------+-----------+
|  1 | jhon     | smith     |
|  2 | anderson | neo       |
|  3 | trinity  | jackson   |
+----+----------+-----------+
3 rows in set (0.00 sec)

mysql> select * from addresses;
+----+-----------------+---------+
| id | address         | student |
+----+-----------------+---------+
|  1 | Av 1 2nd Street |       1 |
|  2 | Av 3 4 Street   |       2 |
|  3 | St 23 7 Av      |       3 |
+----+-----------------+---------+
3 rows in set (0.00 sec)

mysql> select s.name,s.last_name,a.address from students s join addresses a on a.student=s.id;
+----------+-----------+-----------------+
| name     | last_name | address         |
+----------+-----------+-----------------+
| jhon     | smith     | Av 1 2nd Street |
| anderson | neo       | Av 3 4 Street   |
| trinity  | jackson   | St 23 7 Av      |
+----------+-----------+-----------------+
3 rows in set (0.00 sec)
于 2013-08-13T04:31:57.050 回答
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最好使用数字格式的外键所以用户名应该是StudentDetails表的id。

你能把你试图运行的 SQL Query 放进去吗？

于 2013-08-13T03:29:21.393 回答
0

选项 1：
首先输入地址数据，并在 StudentDetails 中创建行时使用该 ID

选项 2：
更改字段 StudentDetails.Address 使其允许 NULL 值，输入 StudentDetails，然后输入地址，然后更新 StudentDetails.Address

于 2013-08-13T01:00:54.670 回答