Basics of Foreign Keys in MySQL? - Stack Overflow
Is there any good explanation of how to use MySQL's foreign key construct? I don't quite get it from the MySQL docs themselves. Up until now I've been handling things like foreign keys with joins ...
mysql - ERROR 1452: Cannot add or update a child row: a foreign key ...
Feb 9, 2014 · Taken from Using FOREIGN KEY Constraints Foreign key relationships involve a parent table that holds the central data values, and a child table with identical values pointing back to its …
Como adicionar uma foreign key em uma tabela já criada
Jan 30, 2016 · Sou iniciante em mysql e não consigo adicionar uma fk em uma tabela que criei. Tenho duas tabelas (pessoa, objeto) e desejo criar uma 'fk_pessoa' em objeto que receba o valor do …
How can I temporarily disable a foreign key constraint in MySQL?
SET FOREIGN_KEY_CHECKS=1; didn't work for me in PHPMyAdmin because I forgot to uncheck the 'Enable foreign key checks' checkbox. In PHPMyAdmin you can skip these SET commands and just …
mysql - Error Code: 1822. Failed to add the foreign key constaint ...
Oct 13, 2014 · The only data type difference that is permitted between columns in a foreign key relationship is length of a varchar. For example, VARCHAR (10) can reference VARCHAR (20) or …
Can table columns with a Foreign Key be NULL? - Stack Overflow
the foreign key, cannot be null by default in mySQL, the reason is simple, if you reference something and you let it null, you will loose data integrity. when you create the table set allow null to NOT and …
mysql - How do I see all foreign keys to a table or column? - Stack ...
Oct 14, 2008 · In MySQL, how do I get a list of all foreign key constraints pointing to a particular table? a particular column? This is the same thing as this Oracle question, but for MySQL.
mysql - Add Foreign Key to existing table - Stack Overflow
Also, the MySQL manual says: Corresponding columns in the foreign key and the referenced key must have similar internal data types inside InnoDB so that they can be compared without a type …
mysql - SQL keys, MUL vs PRI vs UNI - Stack Overflow
From the MySQL 5.7 documentation: If Key is PRI, the column is a PRIMARY KEY or is one of the columns in a multiple-column PRIMARY KEY. If Key is UNI, the column is the first column of a …
sql - Foreign keys in MySQL? - Stack Overflow
The foreign key column isn't exactly the same data type as the primary key column in the referenced table Unfortunately, MySQL gives no message that it has failed to create the foreign key constraint. It …