For this question, I am referring to the specific case where you have table T, it has primary key K, but K is a foreign key. Is this valid? And how would you write it in SQL99? All the other …
Tag: foreign-keys
How to make a foreign key on a different account
So I am currently using my account with username: ctxsys and a password In this account I have table named archiv11. In another account named d5a11 with a password I have a table called fileLocation …
cannot drop a foreign key in mySQL
It’s a common example between Persons and Orders. I just copied it from Internet as a test. CREATE TABLE Persons ( ID int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(…
What’s the meaning of RESTRICT in Foreign Keys?
There is 4 cases: (For example I’m talking about ON DELETE) CASCADE: the referencing rows will be deleted automatically along with the referenced ones. SET NULL: the value of referencing record will be set to NULL automatically along with the referenced ones. NO ACTION: There will not be any change in t…
error: there is no unique constraint matching given keys for referenced table “incident”
I know that this question has been already answered a million of times, but I couldn’t find any solution. Well I have these three tables on postgres sql. When I try to create the table incident_has_volunteer it throws the error there is no unique constraint matching given keys for referenced table ̶…
Sharing composite foreign key based on the same columns across multiple tables in MS SQL Server
I have database with multiple tables which contains information about different instruments (Currencies, Funds, Equities etc.). All instruments have Type and Id fields which represents unique key for …
SET CONSTRAINTS ALL DEFERRED not working as expected
In a PostgreSQL 9.3 database, if I define tables a and b as follows: And then do the following: It produces the error below. Why is SET CONSTRAINTS not having the desired effect? Answer Only DEFERRABLE constraints can be deferred. Let me suggest superior alternatives first: 1. INSERT in order Reverse the sequ…
PostgreSQL Foreign Key syntax
I have 2 tables as you will see in my PosgreSQL code below. The first table students has 2 columns, one for student_name and the other student_id which is the Primary Key. In my second table called tests, this has 4 columns, one for subject_id, one for the subject_name, then one for a student with the highest…
Foreign Key constraints missing after phpmyadmin export
I create a table in mysql using the following script: When I export the created table from phpMyAdmin, I obtain the following script So the question are: where is my foreign key constraints? does KEY refer to FK? Seems that the two tables utente and attivita are no longer referenced in the new generated scrip…
How to populate a table’s foreign keys from other tables
I’ve got the following tables, of which translation is empty and I’m trying to fill: The source data to fill translation is a temporary table that I’ve populated from an external CSV file: What I’d like to do is to fill translation with the values from tmp_table. The translated field c…