I am designing a mysql database and have come across these relations which will grow in the future.
Suppose Customer is tied to 2 different tables Policies and Options.
Each customer has multiple relationship with policies and likewise with options. Since I am keeping a details and history of the table as well every time I add a relation with customer, I will have to maintain another 2 tables. To calculate the price the customer owes, I will have to go thru customer_policies then customer_options and calculate the total price. Also the number of tables increases as the relationship increases.
If customer has a relation with policies it will have 2 tables -
customer_policies and customer_policies_details.
If customer has one more relation with options, it will add 3 more -
customer_options, and customer_option_history.
Like wise, it will keep on adding 2 more tables if there is one more
relation and the problem grows and grows.
I have tried 2 different options which I have mentioned below. I wanted to know what is the best way to solve this problem so that the table can be maintained as the relation grows.
Option 1:
customer_policies:
CustomerPolicyId CustomerId PolicyId Status
1 1 1 Active
2 1 2 Active
customer_policies_details:
CustomerPolicyDetailsId CustomerPolicyId Price
1 1 10
2 2 20
customer_options:
CustomerOptionId CustomerId OptionId Status
1 1 1 Active
2 1 2 Active
customer_options_details:
CustomerOptionDetailsId CustomerOptionId Price
1 1 10
2 2 20
Option 2:
Create a single table customer_selections and use Type and Id field instead like so:
customer_selections:
CustomerSelctionId CustomerId Type Id Status
1 1 Policy 1 Active
2 1 Policy 2 Active
3 1 Option 1 Active
4 1 Option 2 Active
customer_selection_details:
DetailsId CustomerSelctionId Price
1 1 10
2 2 20
3 3 10
4 4 20
To create a history of this I just have to create a customer_selections_details and keep track of all changes.
There should be better ways to solve this problem.
Related
I'm currently working on a little project that uses MySQL. However I'm struggling with the database design. Currently I've come up with 2 designs, one stores more data but is actually the way I want it to be, however this way makes it really hard to work with the data. The other way is I think more basic and simplifies a lot of things but stores less data.
Design 1
Example data items table
id
description
time_created
1
Car
2021-04-17 17:30:00
2
Bike
2021-04-17 17:30:00
Example data user_items table
id
user_id
item_id
time_achieved
1
1
1
2021-04-17 17:30:04
2
1
1
2021-04-17 17:30:03
3
1
1
2021-04-17 17:30:17
4
1
1
2021-04-17 17:30:22
5
1
1
2021-04-17 17:30:34
6
1
2
2021-04-17 17:30:42
7
1
2
2021-04-17 17:30:54
Design 2
Example data items table
id
description
time_created
1
Car
2021-04-17 17:30:00
2
Bike
2021-04-17 17:30:00
Example data user_items table
id
user_id
item_id
count
1
1
1
5
2
1
2
2
Basically we have items that can be anything, they include a description to specify what they actually are. A user can collect items (a lot). These are stored in the user_items table which contains a FK user_id and item_id to the users and items table. The users table is left out for simplicity.
As you can see design 1 stores a lot more rows for the user_items table, this allows us to add more information (time_achieved and more) per item that a user achieved. However this results in more rows and probably a harder time queriyng. Design 2 on the other hand simply adds a count column to determine how many items the user has, but this is very limiting because we cannot add more data (achieved time..) per user_item.
I'm not sure if design 1 is the right and only design for what we want to achieve. Basically we really want to store additional metadata per user_item but I just don't know if this is the right design since it quickly fills up the database. Does anyone have a suggestion/idea for an alternative design which stores less data than design 1 but still allows to add more info per user_item?
Thanks in advance.
Does anyone have a suggestion/idea for an alternative design which stores less data than design 1 but still allows to add more info per user_item?
Design 1 should work.
This design will also work but quickly fills up, more efficient.
id, item_id,Item_des,Item_qty,user_id,username,time_created all in one table.
some of the values will be repeated.
I'm trying to join a few tables in MySQL. Our setup is a little unique so I try to explain as good as I can.
I have a table 'INVENTORY' that represents the current items on stock.
These items are stored in a table 'COMPONENT'
Components are being used in installations.
Every user can have multiple installations and the same component can be used in multiple installation as well.
To uniquely map a component to an installation, it can be assigned to a PRODUCT. a product as has a 1-1 relationship with an installation. A component is not directly related to an installation
To finally assign a product to a specific installation a mapping table COMPOMENT_PRODUCT is used.
Example:
A component is like a part, lets say a screw. This screw is used in a computer. The very same screw can be used on multiple computers. But each computer can only be used on one specific installation.
TABLE COMPOMENT_PRODUCT
COMPOMENT_ID PRODUCT_ID
1 1
1 2
2 1
2 2
So we have the components C1 and C2 relevant for two installations.
TABLE INVENTORY
COMPOMENT_ID INSTALLATION_ID ON_STOCK
1 1 5
1 2 2
What I want to achieve
Now, I want to retrieve the inventory state for all components. But, not every component has an inventory record. In these cases, the ON_STOCK value from the inventory shall be NULL
That means, for this example I'd expect the following results
COMPOMENT_ID PRODUCT_ID ON_STOCK
1 1 5
1 2 2
2 1 NULL
2 2 NULL
But executing this query:
SELECT DISTINCT
COMPONENT_PRODUCT.COMPONENT_ID,
COMPONENT_PRODUCT.PRODUCT_ID,
INVENTORY.ON_STOCK
FROM INVENTORY
RIGHT JOIN COMPONENT_PRODUCT ON COMPONENT_PRODUCT.COMPONENT_ID =
INVENTORY.COMPONENT_ID
returns the following resultset:
COMPONENT_ID PRODUCT_ID ON_STOCK
1 1 5
1 2 5
1 1 2
1 2 2
2 1 (null)
2 2 (null)
Now, my next thought was, "of course, this is how joins behave, okay I need to group the results". But the way SQL works, the aggregation is not entirely predictable. SO when I
GROUP BY COMPONENT_PRODUCT.COMPONENT_ID,COMPONENT_PRODUCT.PRODUCT_ID
I get this result:
COMPONENT_ID PRODUCT_ID ON_STOCK
1 1 5
1 2 5
2 1 (null)
2 2 (null)
I have prepared a Fiddle here: http://sqlfiddle.com/#!9/71ca87
What am I forgetting here? Thanks in advance for any pointers.
Try this query -
SELECT DISTINCT
COMPONENT_PRODUCT.COMPONENT_ID,
COMPONENT_PRODUCT.PRODUCT_ID,
INVENTORY.ON_STOCK
FROM INVENTORY
RIGHT JOIN COMPONENT_PRODUCT ON COMPONENT_PRODUCT.COMPONENT_ID =
INVENTORY.COMPONENT_ID
AND COMPONENT_PRODUCT.PRODUCT_ID = INVENTORY.INSTALLATION_ID
I'm building a e-Commerce platform (PHP + MySQL) and I want to add a attribute (feature) to products, the ability to specify (enable/disable) the selling status for specific city.
Here are simplified tables:
cities
id name
==========
1 Roma
2 Berlin
3 Paris
4 London
products
id name cities
==================
1 TV 1,2,4
2 Phone 1,3,4
3 Book 1,2,3,4
4 Guitar 3
In this simple example is easy to query (using FIND_IN_SET or LIKE) to check the availability of product for specific city.
This is OK for 4 city in this example or even 100 cities but will be practical for a large number of cities and for very large number of products?
For better "performance" or better database design should I add another table to table to JOIN in query (productid, cityid, status) ?
availability
id productid cityid status
=============================
1 1 1 1
2 1 2 1
3 1 4 1
4 2 1 1
5 2 3 1
6 2 4 1
7 3 1 1
8 3 2 1
9 3 3 1
10 3 4 1
11 4 3 1
For better "performance" or better database design should I add
another table
YES definitely you should create another table to hold that information likewise you posted rather storing in , separated list which is against Normalization concept. Also, there is no way you can gain better performance when you try to JOIN and find out the details pf products available in which cities.
At any point in time if you want to get back a comma separated list like 1,2,4 of values then you can do a GROUP BY productid and use GROUP_CONCAT(cityid) to get the same.
Supoose I have the following:
tbl_options
===========
id name
1 experience
2 languages
3 hourly_rate
tbl_option_attributes
=====================
id option_id name value
1 1 beginner 1
2 1 advanced 2
3 2 english 1
4 2 french 2
5 2 spanish 3
6 3 £10 p/h 10
7 3 £20 p/h 20
tbl_user_options
================
user_id option_id value
1 1 2
1 2 1
1 2 2
1 2 3
1 3 20
In the above example tbl_user_options stores option data for the user. We can store multiple entries for some options.
Now I wish to extend this, i.e. for "languages" I want the user to be able to specify their proficiency in a language (basic/intermediate/advanced). There will also be other fields that will have extended attributes.
So my question is, can these extended attributes be stored in the same table (tbl_user_options) or do I need to create more tables? Obviously if I put in a field "language_proficiency" it won't apply to the other fields. But this way I only have one user options table to manage. What do you think?
EDIT: This is what I propose
tbl_user_options
================
user_id option_id value lang_prof
1 1 2 null
1 2 1 2
1 2 2 3
1 2 3 3
1 3 20 null
My gut instinct would be to split the User/Language/Proficiency relationship out into its own tables. Even if you kept it in the same table with your other options, you'd need to write special code to handle the language case, so you might as well use a new table structure.
Unless your data model is in constant flux, I would rather have tbl_languages and tabl_user_languages tables to store those types of data:
tbl_languages
================
lang_id name
1 English
2 French
3 Spanish
tbl_user_languages
================
user_id lang_id proficiency hourly_rate
1 1 1 20
1 2 2 10
2 2 1 15
2 2 3 20
3 3 2 10
Designing a system that is "too generic" is a Turing tarpit trap for a relational SQL database. A document-based database is better suited to arbitrary key-value stores.
Excepting certain optimisations, your database model should match your domain model as closely as possible to minimise the object-relational impedance mismatch.
This design lets you display a sensible table of user language proficiencies and hourly rates with only two inner joins:
SELECT
ul.user_id,
u.name,
l.name,
ul.proficiency,
ul.hourly_rate
FROM tbl_user_languages ul
INNER JOIN tbl_languages l
ON l.lang_id = ul.lang_id
INNER JOIN tbl_users u
ON u.user_id = ul.user_id
ORDER BY
l.name, u.hour
Optionally you can split out a list of language proficiencies into a tbl_profiencies table, where 1 == Beginner, 2 == Advanced, 3 == Expert and join it onto tbl_user_languages.
i'm thinking it's a mistake to put "languages" as an option. while reading your text it seems to me that english is an option, and it might have an attribute from option_attributes.
I have a table User that stores user information - such as name, date of birth, locations, etc.
I have also created a link table called User_Options - for the purpose of storing multi-value attributes - this basically stores the checkbox selections.
I have a front-end form for the user to fill in and create their user profile. Here are the tables I have created to generate the checkbox options:
Table User_Attributes
=====================
id attribute_name
---------------------
1 Hobbies
2 Music
Table User_Attribute_Options
======================================
id user_attribute_id option_name
--------------------------------------
1 1 Reading
2 1 Sports
3 1 Travelling
4 2 Rock
5 2 Pop
6 2 Dance
So, on the front-end form there are two sets of checkbox options - one set for Hobbies and one set for Music.
And here are the User tables:
Table User
========================
id name age
------------------------
1 John 25
2 Mark 32
Table User_Options
==================================================
id user_id user_attribute_id value
--------------------------------------------------
1 1 1 1
2 1 1 2
3 1 2 4
4 1 2 5
5 2 1 2
6 2 2 4
(in the above table 'user_attribute_id' is the ID of the parent attribute and 'value' is the ID of the attribute option).
So I'm not sure that I've done all this correctly, or efficiently. I know there is a method of storing hierarchical data in the same table but I prefer to keep things separate.
My main concern is with the User_Options table - the idea behind this is that there only needs to be one link table that stores multi-value attributes, rather than have a table for each and every multi-value attribute.
The only thing I can see that I'd change is that in the association table, User_Options, you have an id that doesn't seem to serve a purpose. The primary key for that table would be all three columns, and I don't think you'd be referring to the options a user has by an id--you'd be getting them by user_id/user_attribute_id. For example, give me all the user options where user is 1 and user attribute id is 2. Having those records uniquely keyed with an additional field seems extraneous.
I think otherwise the general shape of the tables and their relationships looks right to me.
There's nothing wrong with how you've done it.
It's possible to make things more extensible at the price of more linked table references (and in the composition of your queries). It's also possible to make things flatter, and less extensible and flexible, but your queries will be faster.
But, as is usually the case, there's more than one way to do it.