MySQL foreign key NULL allowed

You can solve this by allowing NULL in the foreign key column tblImageFlags.resolutionTypeID. PS Bonus points to whomever tells me whether, in the case of databases, it's indexes or indices. The plural of index should be indexes. According to Modern American Usage by Bryan A. Garner MySQL foreign key to allow NULL? Posted by: admin November 1, 2017 Leave a comment. Questions: I'm piecing together an image website. The basic schema's pretty simple MySQL, but I'm having some trouble trying to represent possible admin flags associated with an image (inappropriate, copyrighted, etc.). My current notion is as follows: tblImages ( imageID INT UNSIGNED NOT NULL.

Is it possible to allow NULL values in foreign key? Yes if the FOREIGN KEY column is NULLABLE. The PRIMARY KEY column must be NOT NULL. Example - ProductSubcategoryID is an FK: SELECT ProductName=Name, ProductSubcategoryID FROM AdventureWorks2008.Production.Product /*. ProductName ProductSubcategoryID Tension Pulley NULL Rear Derailleur Cage NULL HL Road Frame - Black, 58 14 HL Road Frame - Red, 58 14. * #1452 - Cannot add or update a child row: a foreign key constraint fails (`mda/artifact`, CONSTRAINT `fk_artifact_feature` FOREIGN KEY (`site_code`, `feature_num`) REFERENCES `feature` (`site_code`, `feature_num`) ON UPDATE CASCADE). I want feature_num in the artifact table to be null because not all artifacts will have a feature associated with it. If they do, it should be a feature that exists in the feature table. How do I make this happen Agree with @Nikola. As you can see here, NULL is allowed in a foreign key field: sqlfiddle.com/#!3/ab003. However, if you use the string 'NULL' as the value, I generate the same error message you are getting: sqlfiddle.com/#!3/ab003 A foreign key is a column or group of columns in a table that links to a column or group of columns in another table. The foreign key places constraints on data in the related tables, which allows MySQL to maintain referential integrity. Let's take a look at the following customers and orders tables from the sample database Setting foreign key references to NULL is very easy to do with SQL 2005 and above. We simply set the foreign key's ON DELETE clause to SET NULL and it will work just as we'd expected

database - MySQL foreign key to allow NULL? - Stack Overflo

To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY constraint on multiple columns, use the following SQL syntax: MySQL / SQL Server / Oracle / MS Access Zur Benennung einer FOREIGN KEY-Einschränkung zu erlauben und für eine FOREIGN KEY-Einschränkung auf mehrere Spalten definieren, verwenden Sie die folgende SQL-Syntax: MySQL / SQL Server / Oracle / MS Access

MySQL foreign key to allow NULL? - ExceptionsHu

Is it possible to allow NULL values in foreign key

sql server - Allowing Foreign Key to be Null - Database

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