I have a problem with this very simple sql statement:
SELECT * FROM video NATURAL JOIN user
I get a warnig ins phpMyAdmin, that there is no unique column in the selection and i cannot edit any values.
But the id column should be unique...
My database structure:
structure 1
structure 2
id in video is a primary key.
id in all other tables are foreign keys pointing to video.id
Could you tell me what is wrong in my structure?
Thanks!
Benjamin
SOLVED:
I created a view from my SQL selection. Inside the view I was able to do changes.
Related
Hi, I'm designing a item catalog using MySQL and Squalize ORM (NodeJS).
Suppose I have a product list with different attributes based on its category (attributes_id in this case).
I would like to get a product by using a JOIN statement with an appropriate attribute table. The design should be scalable as we will have more than a hundred attribute tables.
Roughly the statement will look like this:
JOIN
if ( product.attributes_id == 1 ) 'attributes_car'
elseif ( product.attributes_id == 2 ) 'attributes_food'
BUT the the number of elseif cases will grow more than a hundred later.
So the question is how to design attributes_id? Is it a good idea to make it a foreign key to the database metadata (like INFORMATION_SCHEMA) to point to another table? Should I introduce another table to manage such relationship?
One of option is a Dynamic SQL but I don't think it is a good idea because the ifelse cases should grow.
Or should I give up designing a query and just implement such logic on NodeJS side using ORM?
Thank you!
One solution would be to create an additional table that stores attribute_id and table_name.
Create table attibute_tablename(
attribute_id int(11),
table_name varchar(25),
PRIMARY KEY (attribute_id, table_name)
)
You can also add a foreign key to the product table if you want.
Then you only need an insert to this table for every new item added
I have one table
program(p_id(pk), program_name)
and three other tables:
graduate_survey(id(pk),PO1_avg,PO2_avg,program_name,session),
alumni_survey(id(pk),PO1_avg,PO2_avg,program_name,session),
faculty_survey(id(pk),PO1_avg,PO2_avg,program_name,session)...
I have to link the three tables with program table...How to link these tables in MySQL? graduate_survey, alumni_survey, faculty_survey are some forms which is calculated for some specific program...If in the forms graduate_survey, alumni_survey, faculty_survey there is no text box for entering the program_name, but if i made a column name 'program_name' in the database tables, can i enter the program_name by referencing to the program table? Is there will be any join query?
Use the program id as foreign key in the other tables, like so:
program(p_id(pk), program_name)
graduate_survey(id(pk),PO1_avg,PO2_avg,p_id(fk),session),
alumni_survey(id(pk),PO1_avg,PO2_avg,p_id(fk),session),
faculty_survey(id(pk),PO1_avg,PO2_avg,p_id(fk),session)
You don't really need the program name for the sake of the FK constraints but it's still a nice to have at some point, maybe.
This way you can easily join based on p_id, for instance:
"SELECT * FROM program INNER JOIN graduate_survey ON program.p_id=graduate_survey.p_id WHERE <your condition here>"
Hope this helps.
I am creating a demo application. I am stuck in a scenario, I am not getting the exact way and query to fetch data from sql database in the following scenario:
I have a table named RegistrationTable, this table has a column RegistrationId as its primary key. There is another table named ApplicationDetails, this table has a column ApplicationId as its primary key.
I have referenced ApplicationId as Foreign key to RegistrationId column.
My requirement is, single user can apply to multiple jobs. job details will be present in ApplicationDetails table.
How can I check to how may jobs the user has applied based on his email id stored in registration table.
I have a column Status in ApplicationDetails table, where as soon as user applied to a job I am updating the status column.
I am trying the following query but its not working:
SELECT Status FROM ApplicationDetails
INNER JOIN RegistrationTable ON ApplicationTable.ApplicationId = RegistrationTable.RegistrationId
WHERE RegistrationTable.EmailId = "abc#xyz.com";
Can any one please suggest me how can I go about this. I am a beginner to SQL. Please do suggest a way to solve this. Thanks in advance.
You need to change the table name in your query to ApplicationDetails. This is what you mentioned in your post
SELECT Status FROM ApplicationDetails
JOIN RegistrationTable ON ApplicationDetails.ApplicationId = RegistrationTable.RegistrationId
WHERE RegistrationTable.EmailId = "abc#xyz.com";
I have a situation where I am trying to get a value stored in one table, but have to go through several other tables on the same database to get the correct result.
Table 1 has a PK ID I can query, this PK will give me a new FK in table 2, this will give me a key to table 3 and table 3 will give me key to table 4 that has the value stored against the PK in table 1. If this made sense? I can not do something with the tables or the database, so I need to find a way to select the value in table 4 from the primary key I got in table 1.
Any ideas?
Edit 1 :
I will try to explain better. I have a filepath located in table 4. To get the correct filepath I need to first find the a project id in table 1. That same project id is a FK in table 2. In table 2 I need to find another id (let's call it "customer id") using project id as FK, the customer id is a FK in table 3. In table 3 I need to find purchase id using customer id as FK, the purchase id is a FK in table 4. With the correct FK (purchase id) in table 4, I am able to get the correct filepath. The filepath that coresponds with the project id from table 1.
I am using ASP.NET (Entity Framework) and a SQL database. I was thinking to use Linq, but is somewhat confused about how to do it. Join several tables or try to get the filepath that way?
Did this make it more clear?
use Linq join Query,..
One example, See here
Entity Framework Join 3 Tables
or search LINQ join in Google,you can find the solution yourself.
I need tips when it comes to designing tables in a database. I am designing an employee meal system that monitors and processes meal logs of employees (like an attendance) My problem is here, I have 2 tables: The employee_table and the log_table. The employee table contains basic employee information and it has a unique key (not a primary one) which is employee_number. And then, there's another table, log_time, which contains the swipe data of the employees. Now, the two tables contain and employee_number column. How do I make relation out of them? Can I bind them together so that when I call for the employee_number column on the log_time it will get the basic information of the employee on the other table as well? Sorry because I'm having a hard time when it comes to designing a database.
SQL syntax for a relation might look something like this:
CREATE TABLE employee_table(
FOREIGN KEY (employee_number) REFERENCES employees(number),
...other stuff...
)
With another table that looks like
CREATE TABLE employees(
number INT(10) NOT NULL
)
Here's a great site on SQL foreign keys:
http://www.sitepoint.com/mysql-foreign-keys-quicker-database-development/