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Mysql can parse the foreign key syntax for the myisam table type (meaning no error message will be raised if it encounters an fk definition), making migration from other database products or table engines easier because you do not have to edit the create table statements to remove them.
8 kwi 2019 · REFERENCED_TABLE_NAME = 'airports'; -- <table> flights, carriers, planes. Show all the foreign keys pointing FROM 'mytable': SELECT * FROM information_schema.TABLE_CONSTRAINTS. WHERE information_schema.TABLE_CONSTRAINTS.CONSTRAINT_TYPE = 'FOREIGN KEY'.
Algorithm. The basic algorithm for this task would be as follows: for each table in the schema. for each column in the table. look for another table whose name and primary key name match the current column name. if such a table is found, add a foreign key referencing it.
The recommended engine to use foreign keys is InnoDB, and honestly, for 99% of cases InnoDB is better. You can easily change all your database to use InnoDB instead of MyISAM: add default_storage_engine = InnoDB to /etc/mysql/my.cnf (or equivalent)
MySQL FOREIGN KEY Constraint. The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in another table.
A foreign key constraint is defined on the child table. The essential syntax for a defining a foreign key constraint in a CREATE TABLE or ALTER TABLE statement includes the following: [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (col_name, ...)
This tutorial introduces you to MySQL foreign key constraints and shows you how to manage foreign keys effectively.
