I have two table now:
conference table: id, name
people table: people_id, name
what I want to do
I want to make a new table so that I can get all attend people by conference id but also get all conference a specific man attended by people_id.
what I have thought
make a new table whose columns is all the people's id, and insert each conference as row, if the people shows in conference, we make it 1, otherwise 0. But it's too sparse and difficult to show which people attend a specific conference because we have many columns.
UPDATE
thanks for your comment. Now I create a table like this:
I think it's much better than the table before.
How about this?
A join table called conferences_people.
cp_id | conference_id | people_id
-------+---------------+-----------
1 | 1234 | 1
2 | 1234 | 4
3 | 1234 | 5
Related
the first is the sectors table that has an id and sector name like this
id | sector
1 | Government
2 | Education
The second is the employee table like this (simplified)
Id | name
1 | sam
2 | tom
Finally I have a sectorMap table (this is used to join the two tables above together) like this
Id | sectorid | employeeid
1 | 1 | 2
2 | 1 | 1
3 | 2 | 2
So in this instance, once I join everything together and view the sectors or each employee, it would show that tom has two sectors (government, education) and sam only has one (government)… hope that makes sense
My question is, within my application, the user has the ability to change these sectors by selecting from a multiple selection dropdown in html. For some reason I thought that by doing an update on duplicate expression would work, however seeing how I have multiple rows of data, I would need to delete all rows within the sectormap table that do not reflect the new selection and contain the selected employees id. What would be the best way of going about that?
For instance, in this case, lets say I open the application and see that tom has two sectors tied to him (government, education) and I only wanted him to have one (government). When I deselect education and select GO. The application returns a list to the server that contains (‘government’). How can I formulate an expression to delete the education sector row from the sectormap table that contains his id?
Your answer is in your question.
1st when you are deselecting education. You will get data of (‘government’). right?
So just invert your query. select those records which is not (‘government’), those are education.
So, education records are you can delete.
Hope this will help you. thanks:)
I am working on database for scoring system for my friend. I have table with games and second table with names of sports (footbal, tenis, floorball). I want to store scores of the games but I don't know how to design database for specific needs of scores.
For example:
Football score - 1:2, 2:2 (1st and 2nd half)
Tenis sets - 6:4, 7:6
Floorbal - 1:0, 3:0, 3:2 (1st, 2nd and 3rd part of the game)
I need this score linked to games table, but I need specific table columns for storing score for every game.
I think about:
Multiple tables and and foreign key, but this is not possible in mysql.
Then I think about storing data in json in one row and then parse it specifically based on sport, but probably this is not very good solution.
The only problem from my point of view is:
How create table/s for storing scores in different format based on type of sport?
Thank you for any help
E.g.:
match_id | period_id | team1_score | team2_sore
1 | 1 | 1 | 2
1 | 2 | 2 | 2
2 | 1 | 6 | 4
2 | 2 | 7 | 6
3 | 1 | 1 | 0
3 | 2 | 3 | 0
3 | 3 | 3 | 2
You mention MySQL, so it appears that you want to develop a relational database.
The first step is to define the relations. Based on your example.
A game has one sport.
A sport has zero or more games.
A game has one or more period scores.
A period score has one game.
Based on these relationships, we can define 3 tables.
Sport
-----
Sport ID
Sport name
...
Game
----
Game ID
Sport ID
Game name
PeriodScore
-----------
PeriodScore ID
Game ID
Period
Score
The primary ID fields are known as blind keys. They are auto-incrementing integers. Their sole purpose is to tie the game with the sport, and the period scores with the game. Otherwise, they have no meaning at all. The primary ID fields are the primary (clustering) keys of their respective tables.
The Sport ID in the Game table is a foreign key. This key points back to the Sport table, so you can get the name of the sport. You can create a unique index on (Sport ID, Game ID) if you ever want a list of the games for a particular sport.
The Game ID in the PeriodScore table is another foreign key. You must create a unique index on (Game ID, PeriodScore ID) so that you can retrieve the period scores in the correct order.
When you want to create a relational database, you first define the relationships, then go through a process of normalization.
Sorry if my question seems unclear, I'll try to explain.
I have a column in a row, for example /1/3/5/8/42/239/, let's say I would like to find a similar one where there is as many corresponding "ids" as possible.
Example:
| My Column |
#1 | /1/3/7/2/4/ |
#2 | /1/5/7/2/4/ |
#3 | /1/3/6/8/4/ |
Now, by running the query on #1 I would like to get row #2 as it's the most similar. Is there any way to do it or it's just my fantasy? Thanks for your time.
EDIT:
As suggested I'm expanding my question. This column represents favourite artist of an user from a music site. I'm searching them like thisMyColumn LIKE '%/ID/%' and remove by replacing /ID/ with /
Since you did not provice really much info about your data I have to fill the gaps with my guesses.
So you have a users table
users table
-----------
id
name
other_stuff
And you like to store which artists are favorites of a user. So you must have an artists table
artists table
-------------
id
name
other_stuff
And to relate you can add another table called favorites
favorites table
---------------
user_id
artist_id
In that table you add a record for every artist that a user likes.
Example data
users
id | name
1 | tom
2 | john
artists
id | name
1 | michael jackson
2 | madonna
3 | deep purple
favorites
user_id | artist_id
1 | 1
1 | 3
2 | 2
To select the favorites of user tom for instance you can do
select a.name
from artists a
join favorites f on f.artist_id = a.id
join users u on f.user_id = u.id
where u.name = 'tom'
And if you add proper indexing to your table then this is really fast!
Problem is you're storing this in a really, really awkward way.
I'm guessing you have to deal with an arbitrary number of values. You have two options:
Store the multiple ID's in a blob object in JSON format. While MySQL doesn't have JSON functions built in, there are user defined functions that will extract values for you, etc.
See: http://blog.ulf-wendel.de/2013/mysql-5-7-sql-functions-for-json-udf/
Alternatively, switch to PostGres
Add as many columns to your table as the maximum number of ID's you expect to have. So if /1/3/7/2/4/8/ is the longest entry, have 6 columns in your table. Reason this is bad: you'll have sparse columns that'll unnecessarily slow your tables.
I'm sure you could write some horrific regex to accomplish the task, but I caution on using complex regex's on enormous tables.
Still working on a web application as a school project, and it just seems to keep expanding.
I have to add a layer for teachers so they can manage and coach students through the application. So, I have to link teachers to their students.
I was wondering what the best way would be to do this. I have one table for all users at the moment. The bare basics of this table are:
id | email | firstname | lastname | role
1 | s#s.s | dromiceio | mimus | 1
2 | d#d.d | tyranno | saurus | 2
3 | a#a.a | utah | raptor | 1
Role is the number I assign to them to give them certain permissions. 1 = student, 2 = teacher, 3 = admin.
Assuming that one student has one teacher but one teacher has many students, what would be the best way to design my database table?
I was thinking of creating a new table and just putting the student/teacher ids in it:
For example, if teacher Tyranno Saurus (id 2) has the two students in the table above linked to him, I would make a table like this:
pk_id | teacherid | studentid
1 | 2 | 1
2 | 2 | 3
That way, I would know that teacher Tyranno (id 2) has two students, namely the student with userid 1 and userid 3.
Then again, I have never really worked on anything like this so I was wondering if anyone could give me some insight about this and if it's possible to do this in a better way.
I'm building my app in PHP (CodeIgniter) with MySQL; if that's of importance.
Thanks a lot.
If a student has zero-or-one teacher coaching them, then I would suggest adding a CoachID column to the student table that is a foreign-key to that particular teacher. The intermediate table you've suggested doesn't do anything to simplify this simple relationship, it actually makes it that little bit more complicated.
If you were tying students to classes (where each class has multiple students and each student takes multiple classes) then an intermediate many-to-many mapping table would be a must.
the question is :
i have a table that contains details, this table is used by users when they registered or update there profile or participate in different exams.
The report I need will have some calculation like aggregate scores .
I would to as if it is better to create new table witch includes the report i need or it's better to work on the same table.
Are you able to provide any further details? What fields are available in the table that you want to query? How do you want to display this information? On a website? For a report?
From what you describe, you need two tables. One table (lets call is 'users') would contain information about each user, and the other would contain the actual exam scores (lets call this table 'results' ).
Each person in the 'user' table has a unique ID number (I'll call it UID) to identify them, and each score in the 'results' table also has the UID of person the score relates to. By including the UID of the user in the 'results' table you can link an infinite number of results (known as a one-to-many relationship).
The 'user' table could look like this:
userUID (UID for each person) | Name | User Details
1 | Barack Obama | President
2 | George Bush | Ex-President
The 'results' table could look like this:
UID for each exam | userUID (UID of the person who look the test) | Score
1 | 1 | 85
2 | 2 | 40
3 | 1 | 82
4 | 2 | 25
I always like to add a UID for things like the exam because it allows you to easily find a specific exam result.
Anyway... a query to get all of the results for Barack Obama would look like this:
SELECT Score From 'results' WHERE userUID = 1
To get results for George Bush, you just change the userUID to 2. You would obviously need to know the UID of the user (userUID) before you ran this query.
Please note that these are VERY basic examples (involving fictional characters ;) ). You could easily add an aggregated score field to the 'user' table and update that each time you add a new result to the 'results' table. Depending upon how your code is set up this could save you a query.
Good luck - Hopefully this helps!