I have a database table which contains recipe information, I then have a second table which contains user information and finally I have another table which is a junction table between the two containing recipe_id and user_id which is used to hold the user's saved recipes.
My tables look like this:
|user |
|user_id |
|user_name |
|user_email |
|user_password|
|recipe|
|recipe_id|
|recipe_name|
|recipe_descript|
|category_id|
| etc.|
|user_saved_recipes|
|user_saved_recipe_id|
|user_id|
|recipe_id|
|category|
|category_id|
|category_name|
I want to be able to SELECT recipes from the recipe table that are LIKE recipes from the user_saved_recipes table based on a particular user. If anyone could help me go about this I would be very grateful as I have been struggling to find a solution.
Basically I want to be able to get a list of recipes that are similar to those recipes the user has saved thus creating suggestions for the user.
This is what I have tried so far:
SELECT *
FROM recipe r
JOIN user_saved_recipes ur
ON r.recipe_id = ur.recipe_id
JOIN user u
ON ur.user_id = u.user_id
WHERE ur.user_id = 1;
I know I need a LIKE in there somewhere in order to return rows with a similar name but I am unsure of how to go about this as I only have recipe_id in the user_saved_recipes junction table.
Thanks!
Recipes that are "like" other recipes is a very vague request. You have to consider - and specify - how you will calculate "like" in this case. What are some typical use cases you wish to meet? e.g.
Consider that someone really likes rabbit as an ingredient;
"You may also like" suggestions from your software should include other rabbit recipes.
So matching on ingredients (particularly the "hero" ingredient) is very likely to part of your algorithm.
Similarly, if a person has saved several cakes in their favourites, then the category cake will likely be a useful part of that algorithm.
Basically you need to compute a rank you can apply to recipes not already in their favourites that share some characteristics with those within the favourites.
Related
Suppose I have a database called clubmembership that has a column for names, a column for clubs, and a column for the role they play in that club. The name Margrit would be in the column name many times, or as many times as she is in a club. If I want to see which people are members of the sewing club my query might look something like this:
SELECT DISTINCT NAME FROM CLUBMEMBERSHIP
WHERE CLUB=’SEWING’
AND ROLE=’MEMBER’;
My problem is that I can't figure out a query for who is not in the sewing club. Of course the simple 'not in' clause isn't working because there are plenty of rows which sewing does not appear in. In this database if someone is not in the sewing club, sewing does not appear under club so I imagine there is a way to join the different rows with the same name under 'name' and then potentially use the 'not in' clause
I hope this was a good explanation of this question. I have been struggling with this problem for a while now.
Thanks for your help!
Nicolle
This is not something that can be solved by just changing the existing code, it is to do with the database design.
Database normalisation is the process of sorting out your database into sensible tables.
If you’re adding a person many times, then you should create a table called members instead. And if there is a list of clubs, then you should create a clubs table.
Then, you can create a table to join them together.
Here’s your three tables:
members
-------
id (int)
name (varchar)
clubs
-------
id (int)
name (varchar)
memberships
-------
member_id (int)
club_id (int)
Then you can use joins in MySQL to return the information you need.
Stack Overflow doesn’t like external links as the answer should be here, but this is a huge topic that won’t fit in a single reply, so I would briefly read about database normalization, and then read about ‘joining’ tables.
If I understand you correctly, you wanted to list all names that is not a member of SEWING. The Inner query will get all Names that are member of SEWING, however, the NOT EXISTS operator will get all Names that are not found in the inner query.
SELECT DISTINCT C.NAME
FROM CLUBMEMBERSHIP C
WHERE C.ROLE = 'MEMBER'
NOT EXISTS
(
SELECT NULL
FROM CLUBMEMBERSHIP D
WHERE D.CLUB='SEWING'
AND D.ROLE='MEMBER'
AND C.NAME = D.NAME
)
Here's a Demo.
I have read various topics regarding table relations and while i am building my database i am a bit confused on what should i do.
I have 3 type of registration on my site(artist, fan, companies). Each registered user gets a unique key and username and the appropriate type of user (ex. fan). I am trying to involve music genres to all types of registration but genres will also be added to uploaded music files. At the moment i am storing one music genre per track and user by an array list that is shown in a form. Then system is storing it to the appropriate field. But i want some users to have more than 1 genres stored.
Now what i have done is below:
Users table (total 14 columns)
ID | username | email | password | type | signup | lastlogin | etc.
Settings table (total 10 columns)
ID | username | description | banner | country | genres | avatar etc.
Music table
ID | username | artist | title | maingenre | othergenre | cover | fileurl
By having in mind performance and let's assume that thousand of thousand users is registering...
Should i just add all settings column in the users table or it's ok to keep as i have them now? Settings can be updated by user while users table is updated by the system.
Should i split the user table according to users type? For example Artist table, fan table etc. that will store the appropriate registration and settings? Type of user needs to be in a column as is important for some functions of the site.
Regarding music table i was thinking to making a table for each genre that will store the uploads according to the genre specified by the user. Is this a good way of storing tracks to database or not? So when i want to call tracks of disco music i just use the disco music table.
Any help will be much appreciated.
not quiet sure I understand everything completely how your table is correlated, or what exactly you want or plan to do, but here is one idea about how to store genres in your database. And to connect it with your Setting table
First create table Genres in which you will store all genres. That table could look like this
Table: Genres
ID | genres_name | description etc.
ID - will be primary key auto increment
genres_name - will hold the name of genre (blues, jazz, disco...)
description - this column i added just if you want to add something specific by every genre it's not necessary
Next step is to create table Settings_genres. This table will store relation between your Setting table and Genres table and will look like this
Table: Settings_genres
settings_id | genres_id
So data in this table will look like this (for the setting ID 1 which will have 3 different Genres)
settings_id | genres_id
------------------------
1 | 2
------------------------
1 | 4
------------------------
1 | 5
------------------------
settings_id and genres_id will be primary key pair which means that you wont be able to store two identical pair int this table (You can have only one relation between one settings column and one genre column)
That is something called Many to many relationship and I'm sure that you can easily find more about that if you google it just a little.
When you want to pull data off from database which will show all settings and all genres you can do it with query like this
SELECT Settings.*, Genres.genres_name, Genres.description
FROM Settings
INNER JOIN Settings_Genres
ON Settings.ID = Settings_Genres.settings_id
INNER JOIN Genres
ON Settings_Genres.genres_id = Genres.ID
ORDER BY ID
Here is SQL Fiddle to see how it's look like.
When you want to pull data from settings table where that table is connected with specific genre you do that like this
SELECT Settings.*, Genres.genres_name, Genres.description
FROM Settings
INNER JOIN Settings_Genres
ON Settings.ID = Settings_Genres.settings_id
INNER JOIN Genres
ON Settings_Genres.genres_id = Genres.ID
WHERE Genres.genres_name = 'Rock'
ORDER BY ID;
This can also be achieved by this query which may be a little faster but let's not go into detail...
SELECT Settings.*, Genres.genres_name, Genres.description
FROM Settings
INNER JOIN Settings_Genres
ON Settings.ID = Settings_Genres.settings_id
INNER JOIN Genres
ON Settings_Genres.genres_id = Genres.ID
AND Genres.genres_name = 'Rock'
ORDER BY ID;
Here is FIDDLE for that...
So basically I suggest you to learn a little bit about relation between tables especially many to many relationship. And on than you will see how to improve your data table design.
Hope I help a little.
GL!
i think the way your table is, is okay. you dont have to split the table based on the type of users you have. but i think what you could use is font end technologies to allow users preform activities you want them, which is restricting them to only what you want them to do, they by controlling flow of information within the system. i hope that helps.
I am having a database design issue and i'm still pretty new to MySQL so I thought I would ask here. What would be the best way to get data for a chronological feed from multiple tables? For example a user does many things, they vote, comment, rate, ask questions. I save all this information in their respective tables "tblVote", "tblRate" etc, now the tricky part. a user can follow a user or many, so say you follow 3-4 people. Following allows you to see their interactions, voting, rating, commenting, asking questions etc in your feed (like facebook or something similar).
What would be the best way to get all the information from all 5 tables for every person they follow and then sort all of that chronologically? I Am assuming my current method (foreach follower grab all votes, comments, ratings etc and sort all would be terrible)
My working theory, so my working idea is to create a Interaction table, that has a column for the users id, the id of the other tables entry, and a type reference. so for example
User ID | InteractionID | Type
9 1232 Comment
10 80 Rating
9 572 Vote
Then you could just go ahead and grab all Interactions for each of the people they follow, sort that and then say grab the top 10? and query the individual databases to get the full info (time of comment, text of comment etc)
A many to many relationship exists between User and Follower. Since, Follower is also another user, this becomes a recursive many-to-many. When you decompose this relationship, you get a Association table or a gerund.
User_Follower {id, userid_fk, followerid_fk}
Both the userid_fk and followerid_fk are referencing to the User table.
Now, I am assuming you have a One-to-many relationship between User-tblRate, User-tblVote, User-tblPost etc.
So, you can write a join something like this:
select p.postTitle, p.postTag, ...,
c.commentId, c.commentData, ...
from (tblUser u INNER JOIN tblPost p
ON (p.userid = u.userid)) INNER JOIN tblComment c
ON (c.userid =
u.userid)
where u.userid in
(select userid_fk from user_follower where followerid_fk = 100)
orderby p.datetime_col ASC, c.datetime_col ASC
LIMIT 10;
100 is the user you want to get the information for.
The idea is that you just have one association table linking the User and Follower, then use simple joins to get the data for all the followees
So I'm new to databases in the scope of the subject and looking for some advice for what I am sure is fairly simple. first I'm using MySql as my db I currently have two tables one for storing user accounts and details :
TABLE user
id | username | password | email_address | user_devices | contact_method
and another for storing video content by producers which looks like:
TABLE series
id | series_title | still_broadcasting | last_updated |
I would like to implement a feature where Users can select series which they wish to be notified of when new releases are made available and also select how to be notified about these releases (email or push notification ) and how often to be notified (on arrival, hourly, daily, weekly ) I am wondering whats the best way to go about doing this?
I've thought of these ideas by myself but am looking for a second opinion/ better way altogether: (all ideas minus 4 involve storing how to notify user along with how often in user table)
adding a text column to user table called following and just having csv's for each series
adding multiple boolean column's to user table one for each series
adding text column to series table with csv's of user's Id numbers following series
creating an entirely new table for notifications though i don't really see the purpose of this as its very redundant
I then plan to just add cron jobs to my server to actually go about regulaurly sending notifications to user's
Thanks in advance for any help.
First of all, it might be worth giving some articles on basic database design a read. A quick google turned up this which covers identifying relationships
http://www.datanamic.com/support/lt-dez005-introduction-db-modeling.html
Your best bet is to use a linking table i.e.
CREATE TABLE userHasSeries (
userID INT,
seriesID INT
);
This can then be used in an INNER JOIN query to get the users choices. What you are doing here is an n:m link between 2 tables. An example inner join would be
SELECT
u.id AS userID,
u.username,
s.seriesID,
s.series_title,
s.still_broadcasting,
s.last_updated
FROM users AS u
INNER JOIN userHasSeries AS uhs
ON uhs.userID = u.id
INNER JOIN series AS s
ON s.id = uhs.seriesID
If users.user_devices is also a comma seperated list I would advise heavily that you adopt a similar n:m approach there also.
A partial answer which complements what has been written in other answers:
Don't keep a list of devices in the 'user_devices' field - break this out into a separate table. In fact, you'll need two tables: one to list the various devices, and one a join table which has two fields: user_id and device_id. This will enable you to track which user has which device, but also to provide a list of users per device.
If I were you I would add a third table as following:
TABLE user
id | username | password | email_address | user_devices | contact_method |notification_type
TABLE series
id | series_title | still_broadcasting | last_updated
TABLE followings
id | user_id | series_id
In notification_type I would put (on arrival, hourly, daily, or weekly), now in the followings tables I will store all the user's preferred series.
Doing this way makes easy to add, delete, update, or select all user's preferred series. All will be simple SQL queries. Also you avoid parsing comma separated strings.
for example, if you want to get all preferred series of an user:
SELECT * FROM followings AS f INNER JOIN series AS s ON f.series_id = s.id WHERE f.user_id = ?
if want to get all users that prefer a serie:
SELECT * FROM followings AS f INNER JOIN user AS u ON f.user_id = u.id WHERE f.series_id = ?
I have a database where users enter their interests. I want to find people with matching interests.
The structure of the interest table is
interestid | username | hobby | location | level | matchinginterestids
Let's take two users to keep it simple.
User Joe may have 10 different interest records
User greg may have 10 different interest records.
I want to do the following algorithm
Take Joe's interest record 1 and look for matching hobbies and locations from the interest database. Put any matching interest id's in the matches field. Then go to joe's interest record 2 etc..
I guess what I need is some sort of for loop that will loop through all of joe's intersts and then do an update each time it finds a match in the interest database. Is that even possible in MySQL?
Further example:
I am Dan. I have 3 interests. Each interest is composed of 3 subjects:
Dan cats,nutrition,hair
Dan superlens,dna,microscopes
Dan film,slowmotion,fightscenes
Other people may have other interests
Joe:
Joe cats,nutrition,strength
Joe superlens,dna,microscopes
Moe
Moe mysql,queries,php
Moe film,specialfx,cameras
Moe superlens,dna,microscopes
Now I want the query to return the following when I log in as Dan:
Here are your interest matches:
--- is interested in cats nutrition hair
Joe is interested in cats and nutrition
Joe and Moe are interested in superlens, dna, microscopes
Moe is interested in film
The query needs to iterate through all Dan's interests, and compare 3,2,1 subject matches.
I could do this in php from a loop but it would be calling the database all the time to get the results. I was wondering if there's a crafty way to do it using a single query Or maybe 3 separate queries one looking for 3 matches, one for 2 and one for 1.
This is definitely possible with MySQL, but I think you may be going about it in an awkward way. I would begin by structuring the tables as follows:
TABLE Users ( userId, username, location )
TABLE Interests( interestId, hobby )
TABLE UserInterests( userId, interestId, level )
When a user adds an interest, if it hasn't been added before, you add it to the Interests table, and then add it to the UserInterests table. When you want to check for other nearby folks with similar interests, you can simply query the UserInterests table for other people who have similar interests, which has all that information for you already:
SELECT DISTINCT userId
FROM UserInterests
WHERE interestId IN (
SELECT interestId
FROM UserInterests
WHERE userId = $JoesID
)
This can probably be done in a more elegant fashion without subqueries, but it's what I thought of now.
As per special request from daniel, although it's kind of duplicate but never mind.
The schema explained
TABLE User (id, username, location )
TABLE Interests(id, hobby )
TABLE UserInterest(userId, interestId, level )
Table users has just user data and a primary key field at the start: id.
The primary key field is a pure link field, the other fields are info fields.
Table Interest again has a primary key that is use to link against and some info field
(ehm well just one, but that's because this is an example)
Note that users and interests are not linked in any way whatsoever.
That's odd, why is that?
Well there is a problem... One user can have multiple intrests and intrests can belong to multiple people.
We can solve this by changing to users table like so:
TABLE users (id, username, location, intrest1, intrest2, intrest3)
But this is a bad, really really bad idea, because:
This way only 3 interests per user are allowed
It's a waste of space if many users have 2, 1 or no interests
And most important, it makes queries difficult to write.
Example query for linking with the bad users table
SELECT * FROM user
INNER JOIN interests ON (user.intrest1 = interests.id) or
(user.intrest2 = interests.id) or
(user.intrest3 = interests.id);
And that's just for a simple query listing all users and their interests.
It quickly gets horribly complex as things progress.
many-to-many relationships
The solution to the problem of a many to many relationship is to use a link table.
This reduces the many-to-many relationship into two 1-to-many relationships.
A: 1 userinterest to many user's
B: 1 userinterest to many interests
Example query using a link-table
SELECT * FROM user
INNER JOIN userInterest ON (user.id = userInterest.userID) //many-to-1
INNER JOIN interest ON (interest.id = userInterest.InterestID); //many-to-1
Why is this better?
Unlimited number of interests per user and visa versa
No wasted space if a user has a boring life and few if any interests
Queries are simpler to maintain
Making it interesting
Just listing all users is not very fun, because then we still have to process the data in php or whatever. But there's no need to do that SQL is a query language after all so let's ask a question:
Give all users that share an interest with user Moe.
OK, lets make a cookbook and gather our ingredients. What do we need.
Well we have a user "Moe" and we have other user's, everybody but not "Moe".
And we have the interests shared between them.
And we'll need the link table userInterest as well because that's the way we link user and interests.
Let's first list all of Moe's Hobbies
SELECT i_Moe.hobby FROM interests AS i_Moe
INNER JOIN userInterests as ui2 ON (ui2.InterestID = i_Moe.id)
INNER JOIN user AS u_Moe ON (u_Moe.id = ui2.UserID)
WHERE u_Moe.username = 'Moe';
Now we combine the select for all users against only Moe's hobbies.
SELECT u_Others.username FROM interests AS i_Others
INNER JOIN userinterests AS ui1 ON (ui1.interestID = i_Others.id)
INNER JOIN user AS u_Others ON (ui1.user_id = u_Others.id)
/*up to this point this query is a list of all interests of all users*/
INNER JOIN Interests AS i_Moe ON (i_Moe.Hobby = i_Others.hobby)
/*Here we link Moe's hobbies to other people's hobbies*/
INNER JOIN userInterests as ui2 ON (ui2.InterestID = i_Moe.id)
INNER JOIN user AS u_Moe ON (u_Moe.id = ui2.UserID)
/*And using the link table we link Moe's hobbies to Moe*/
WHERE u_Moe.username = 'Moe'
/*We limited user-u_moe to only 'Moe'*/
AND u_Others.username <> 'Moe';
/*and the rest to everybody except 'Moe'*/
Because we are using INNER JOIN's on link fields only matches will be considered and non-matches will be thrown out.
If you read the query in english it goes like this.
Consider all users who are not Moe, call them U_others.
Consider user Moe, call him U_Moe.
Consider user Moe's Hobbies, call those i_Moe
Consider other users's Hobbies, call those i_Others
Now link i_Others hobbies to u_Moe's Hobbies
Return only users from U_Others that have a hobby that matches Moe's
Hope this helps.