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Learn how to use the FOREIGN KEY constraint to prevent actions that would destroy links between tables in MySQL. See examples of creating, naming, and dropping FOREIGN KEY constraints on CREATE TABLE and ALTER TABLE statements.
Learn how to define and use foreign key constraints in MySQL, which enforce data integrity and referential integrity across tables. See the syntax, rules, conditions, and examples of creating and dropping foreign key constraints.
Following is the basic syntax of defining a foreign key constraint in CREATE TABLE and ALTER TABLE constraint in MySQL. [CONSTRAINT constraint_name] FOREIGN KEY [foreign_key_name] (col_name, ...) REFERENCES parent_tbl_name (col_name,...) [ON DELETE reference_option] [ON UPDATE reference_option]
Learn how to use the FOREIGN KEY constraint to link two tables together in SQL. See the syntax and examples for creating, naming, and dropping FOREIGN KEY constraints in MySQL and other databases.
Here is the basic syntax of defining a foreign key constraint in the CREATE TABLE or ALTER TABLE statement: FOREIGN KEY [foreign_key_name] (column_name, ...) REFERENCES parent_table(colunm_name,...) In this syntax: First, specify the name of the foreign key constraint that you want to create after the CONSTRAINT keyword.
MySQL supports foreign keys, which permit cross-referencing related data across tables, and foreign key constraints, which help keep the related data consistent. A foreign key relationship involves a parent table that holds the initial column values, and a child table with column values that reference the parent column values.
The essential syntax for a defining a foreign key constraint in a CREATE TABLE or ALTER TABLE statement includes the ... For storage engines that support foreign keys, MySQL rejects any INSERT or UPDATE operation that attempts to create a foreign key value in a child table if there is no matching candidate key value in the ...
