数据库规范化和数据输入（管理员后端）

Question

Take a look at the items table below, as you can see this table is not normalized. Name should in a separate table to normalize it.

mysql> select * from items;
+---------+--------+-----------+------+
| item_id | cat_id | name      | cost |
+---------+--------+-----------+------+
|       1 |    102 | Mushroom  | 5.00 |
|       2 |      2 | Mushroom  | 5.40 |
|       3 |    173 | Pepperoni | 4.00 |
|       4 |    109 | Chips     | 1.00 |
|       5 |     35 | Chips     | 1.00 |
+---------+--------+-----------+------+

This table is not normalize because on the backend Admin site, staff simply select a category and type in the item name to add data quickly. It is very quick. There are hundreds of same item name but the cost is not always the same.

If I do normalize this table to something like this:

mysql> select * from items;
+---------+--------+--------------+------+
| item_id | cat_id | item_name_id | cost |
+---------+--------+--------------+------+
|       1 |    102 |            1 | 5.00 |
|       2 |      2 |            1 | 5.40 |
|       3 |    173 |            2 | 4.00 |
|       4 |    109 |            3 | 1.00 |
|       5 |     35 |            3 | 1.00 |
+---------+--------+--------------+------+
mysql> select * from item_name;
+--------------+-----------+
| item_name_id | name      |
+--------------+-----------+
|            1 | Mushroom  |
|            2 | Pepperoni |
|            3 | Chips     |
+--------------+-----------+

Now how can I add item (data) on the admin backend (data entry point of view) because this table has been normalized? I don't want like a dropdown to select item name - there will be thousands of different item name - it will take a lot of of time to find the item name and then type in the cost.

There need to be a way to add item/data quick as possible. What is the solution to this? I have developed backend in PHP.

Also what is the solution for editing the item name? Staff might rename the item name completely for example: Fish Kebab to Chicken Kebab and that will effect all the categories without realising it. There will be some spelling mistake that may need correcting like F1sh Kebab which should be Fish Kebab (This is useful when the tables are normalized and I will see item name updated every categories).

Answer 1

I don't want like a dropdown to select item name - there will be thousands of different item name - it will take a lot of of time to find the item name and then type in the cost.

There are options for selecting existing items other than drop down boxes. You could use autocompletion, and only accept known values. I just want to be clear there are UI friendly ways to achieve your goals.

As for whether to do so or not, that is up to you. If the product names are varied slightly, is that a problem? Can small data integrity issues like this be corrected with batch jobs or similar if they are a problem?

Decide what your data should look like first, based on the design of your system. Worry about the best way to structure a UI after you've made that decision. Like I said, there are usable ways to design UI regardless of your data structuring.

Answer 2

I think you are good to go with your current design, for you name is the product name and not the category name, you probably want to avoid cases where renaming a single product would rename too many of them at once.

Normalization is a good thing but you have to measure it against your specific needs and in this case I really would not add an extra table item_name as you shown above.

just my two cents :)

Answer 3

What are the dependencies supposed to be represented by your table? What are the keys? Based on what you've said I don't see how your second design is any more normalized that your first.

Presumably the determinants of "name" in the first design are the same as the determinants of "item_name_id" in the second? If so then moving name to another table won't make any difference to the normal forms satisified by your items table.

User interface design has nothing to do with database design. You cannot let the UI drive the database design and expect sensible results.

Answer 4

You need to validate the data and check for existence prior to adding it to see if it's a new value.

$value = $_POST['userSubmittedValue']

//make sure you sanitize the variable (never trust user input)

$query = SELECT item_name_id 
         FROM item_name 
         WHERE name='$value';

$result = mysql_query($query);
$row = mysql_fetch_row($result);

if(!empty($row))
{
//add the record with the id from $row['item_name_id'] to items table
}
else
{
//this will be a new value so run queries to add the new value to both items and item_name tables
}

Answer 5

There need to be a way to add item/data quick as possible. What is the solution to this? I have developed backend in PHP.

User interface issues and database structure are separate issues. For a given database structure, there are usually several user-friendly ways to present and change the data. Data integrity comes from the database. The user interface just needs to know where to find unique values. The programmer decides how to use those unique values. You might use a drop-down list, pop up a search form, use autocomplete, compare what the user types to the elements in an array, or query the database to see whether the value already exists.

From your description, it sounds like you had a very quick way to add data in the first place: "staff simply select a category and type in the item name to add data quickly". (Replacing "mushroom" with '1' doesn't have anything to do with normalization.)

Also what is the solution for editing the item name? Staff might rename the item name completely for example: Fish Kebab to Chicken Kebab and that will effect all the categories without realising it.

You've allowed the wrong person to edit item names. Seriously.

This kind of issue arises in every database application. Allow only someone trained and trustworthy to make these kinds of changes. (See your dbms docs for GRANT and REVOKE. Also take a look at ON UPDATE RESTRICT.)

In our production database at work, I can insert new states (for the United States), and I can change existing state names to whatever I want. But if I changed "Alabama" to "Kyrgyzstan", I'd get fired. Because I'm supposed to know better than to do stuff like that.

But even though I'm the administrator, I can't edit a San Francisco address and change its ZIP code to '71601'. The database "knows" that '71601' isn't a valid ZIP code for San Francisco. Maybe you can add a table or two to your database, too. I can't tell from your description whether something like that would help you.

On systems where I'm not the administrator, I'd expect to have no permissions to insert rows into the table of states. In other tables, I might have permission to insert rows, but not to update or delete them.

There will be some spelling mistake that may need correcting like F1sh Kebab which should be Fish Kebab

The lesson is the same. Some people should be allowed to update items.name, and some people should not. Revoke permissions, restrict cascading updates, increase data integrity using more tables, or increase training.