I got these two tables where one table is having multiple foreign keys to the second table. Table rankings Table item One ranking record may have multiple association to item table using first_item_id, second_item_id, third_item_id or forth_item_id fields. I want to retrieve ranking records with the correspon…
Tag: foreign-keys
How to retrieve all grand parents at once
I have two simple tables in SQLITE3 (family bonds): “persons” (id, fname, lname) “relationships” (parent/child) I would like to get each grand children along with all their grand parents (from 1 to 4 of them depending on the grand child) so that 1 row result = Thanks to Caius Jard, I&#…
Oracle SQL – need to flip values, but don’t know how
This is the output, but I need those values changed. I have ID primary keys for both – kasutaja and riistvara, but I don’t know how to match kasutaja ID 1 with riistvara ID 2 and vice versa. And the output should be like this: The R_NIMETUS and SEERIA_NR fields are different on my output what I ge…
Keep a foreign key NULL if info is easily determine?
I have the following tables: An image can have a country (or not) or a place (or not). Let’s say that I have a record in the country table: And places in the place table: I want to tag an image with the country Spain and a place Barcelona In the image table, should I enter the country_id and the
Django, have model to be related to many instances of itself
I have a model: I want it to have a sub_industries field that will hold all of its sub industries, which should be instances of Industry model. I cannot be ManyToMany because each industry has only one parent industry. Answer You can add a ForeignKey to itself with: You can use NULL/None to express that an in…
Simple database with 3 tables and “no matching unique or primary key for this column”
I have three tables, two are created independently, and the third one is created to include some inputs from the first two. First two tables have no problems, however, when I try to create the third one, I get an error: The thing is, I created the third table by copy/pasting the column names/definitions right…
Is table order imporant in mysql when creating relation between them?
I have quite simple question. I am creating database administration tool, where user will be able to create relations between tables, but I am not sure if table order is important when creating relations. For example: I have two tables ‘user'(user_id(INT, PRIMARY KEY), name(VARCHAR), email(VARCHAR)) and…
Foreign and Primary Key Conceptual Questions
I am a newbie at SQL/PostgreSQL, and I had a conceptual question about foreign keys and keys in general: Let’s say I have two tables: Table A and Table B. A has a bunch of columns, two of which are A.id, A.seq. The primary key is btree(A.id, A.seq) and it has a foreign key constraint that A.id reference…
Inserting data into a table using foreign keys in MySQL
I am trying to insert data into a contacts table using foreign keys in mysql, the structure of tables are as follows The fk_id in the contacts table is the FOREIGN KEY and it relates to the pers_id PRIMARY KEY in the users table, I am trying to insert a new contact with relates to a user in the users
Why does the DBMS say that the primary key is not present in the table
I am a CS student that is taking his first course in databases so here I am using Postgresql to create a database with the following tables: employee, project, and worksOn. So if you run the program you can see that both the employee and project table are created. However, worksOn is not because it gives me t…