I'm trying to learn more about creating "advanced" databases, so my project is to keep track of the wins and losses at a website called SaltyBet. Bots fight against each other and people bet on the outcome. I want to create a database for myself to keep track of each match, where I enter in the values manually.
I have 2 tables:
chars with just an "ID" field and a "name" (unique) field, and
matches with "ID", "player1", "player2", "winner", and "odds".
The way I want it to work is if I go to insert a row into matches, it will create the appropriate character in the chars database, if it doesn't already exist.
I have the following relationships set up within PHPMyAdmin:
Creating this form in the "Insert" view:
This works fine - as long as I have already entered in both characters in the chars table. However, there often isn't enough time to go through 3 different views to create the appropriate characters in the chars table to then use in the matches table. I had the idea to create a trigger, which inserts the characters if they don't exist, but AFAIK I cannot maintain the relationship between the two tables because I cannot enter a new one in matches.
Is there any way I can easily approach this without writing a form in PHP? I'd rather learn how to do it the "proper" way instead of relying on the simple MySQL commands I learned years ago and never expanded on.
Thank you!
I agree that if you want to use a trigger that creates the row in chars after an insert in matches, it won't work because the insert itself will give a problem.
I don't see how you can do it without coding an application that would first verify in chars whether the row exists, insert it if needed, then insert into matches.
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I am currently working on a database project that uses platform MySQL. Project includes tables such as course, instructor, researchArea etc. What I really need is a trigger that checks how many words from "researchArea keywords" are in the given text. Text is going to be pulled from another table which named course. With the result I am planing to get a integer matching percentage value and with the value, I planned to insert the calculated value into "matchingvalue" which is a attribute in instructor table, a attribute to describe the relation of the course content between the instructor.
I have a big lack of scripting experience and syntax information in sql already and I couldn't even think a solution to solve this thing. Any ideas to create a trigger for this query or function whatever it is?
Image of the EER
I am trying to do a CRUD operation with a form and I was wondering if like for example, a student is asked to register for say 4 subjects for an exam and they have to choose from a list, is it possible for those subject to appear in a single row on a column or do I have to create a seperate table for that?
It's generally good practice to add a separate table for that so that you can then use the information to, for example, find out which students need to take the economics exam. If you put comma separated values into a column, it's harder to get that information back.
If you're using newer versions of MySQL (5.7 or later), you could also check out the JSON column type which caters for storing more than just a single value in one column - but I'd still recommend using a separate table in most cases for good data design. Hope that helps!
It is possible. You could for instance write a string 'Math,Literature,Arts'.
However, you should only do this when you are never interested in the separate parts. If you never need a query to ask how many students registered for 'Math' or whether student 123 registered for 'Arts' etc., then no problem.
This would be a very rare case, though. Usually you are interested in the separate subjects, so store them separately, i.e. have a Student table, a subject table, and a student_subject table.
I have a database with two tables. The first one contains the user_name, user_password, user_email. The second one contains the user_name, user_age, user_description.
When a person finds the user he needs by the user_name, the script looks through the database using the user_name, to give out the information about certain user.
But if the person changes his user_name via preferences, the value changes only in the first table.
Question:
1) Is there a way to make the user_name in the second table change automatically? (To connect them some how)
I am using MySQL (phpMyAdmin).
This is just a simple example. In "real world" I am trying to manage more serious applications that have more tables. Is there an easier way than to create a separate php query for each table?
You could always create an AFTER UPDATE MySQL trigger targeting single rows for this. See the manual. It's probably not easier than using separate PHP queries for the tables, though. You don't need to spell them all out, just map up what needs to be synchronized when, and abstract your code.
However I'd recommend that you use a unique ID field for the user and only store the username in one of the tables -- and refer to the user with the ID under the hood of your code, and in both tables. Not a good idea to use something changeable as a unique identifier in your database design.
I've created a table name 'combined_data' using data from two tables 'store_data' and 'hd_data'. The two tables share a common column which I used to link the data when creating the new table and that is 'store_num'. What happens is when a user submits information to 'store_data' I want info from that submit such as store_num, store_name, etc to move into the 'combined_data' table as well as pull information from the 'hd_data' that pertains to the particular store_num entered such as region, division etc. Trying to come up with the structure to do this, I can fill in table names and column names just fine. Just curious if this is doable or if another solution should be sought out?
This is a common situation when saving data and requires to be split into 2 or more different repositories. I would create a stored procedure, and pass everything into a transaction, so if at any time something fails, it would roll back, and you would have consistency between your tables.
However, yes you can also do it with a trigger on insert of data on either store_data, or hd_data, if you would like to keep it simple.
I am pretty new to this so sorry for my lack of knowledge.
I set up a few tables which I have successfully written to and and accessed via a Perl script using CGI and DBI modules thanks to advice here.
This is a member list for a local band newsletter. Yeah I know, tons of apps out there but, I desire to learn this.
1- I wanted to avoid updating or inserting a row if an piece of my input matches column data in one particular column/field.
When creating the table, in phpmyadmin, I clicked the "U" (unique) on that columns name in structure view.
That seemed to work and no dupes are inserted but, I desire a hard coded Perl solution so, I understand the mechanics of this.
I read up on "insert ignore" / "update ignore" and searched all over but, everything I found seems to not just skip a dupe.
The column is not a key or autoinc just a plain old field with an email address. (mistake?)
2- When I write to the database, I want to do NOTHING if the incoming email address matches one in that field.
I desire the fastest method so I can loop through their existing lists export data, (they cannot figure out the software) with no racing / locking issues or whatever conditions in which I am in obvious ignorance.
Since I am creating this from scratch, 1 and 2 may be in fact partially moot. If so, what would be the best approach?
I would still like an auto increment ID so, I can access via the ID number or loop through with some kind of count++ foreach.
My stone knife approach may be laughable to the gurus here but, I need to start somewhere.
Thanks in advance for your assistance.
With the email address column declared UNIQUE, INSERT IGNORE is exactly what you want for insertion. Sounds like you already know how to do the right thing!
(You could perform the "don't insert if it already exists" functionality in perl, but it's difficult to get right, because you have to wrap the test and update in a transaction. One of the big advantages of a relational database is that it will perform constraint checks like this for you, ensuring data integrity even if your application is buggy.)
For updating, I'm not sure what an "update ignore" would look like. What is in the WHERE clause that is limiting your UPDATE to only affect the 1 desired row? Perhaps that auto_increment primary key you mentioned? If you are wanting to write, for example,
UPDATE members SET firstname='Sue' WHERE member_id = 5;
then I think this "update ignore" functionality you want might just be something like
UPDATE members SET firstname='Sue' WHERE member_id = 5
AND email != 'sue#example.com';
which is an odd thing to do, but that's my best guess for what you might mean :)
Just do the insert, if data would make the unique column not be unique you'll get an SQL error, you should be able to trap this and do whatever is appropriate (e.g. ignore it, log it, alert user ...)