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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.
MySQL FOREIGN KEY syntax. 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]
MySQL FOREIGN KEY syntax. Here is the basic syntax of defining a foreign key constraint in the CREATE TABLE or ALTER TABLE statement: [CONSTRAINT constraint_name] FOREIGN KEY [foreign_key_name] (column_name, ...) REFERENCES parent_table(colunm_name,...) [ON DELETE reference_option]
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, ...)
10 lip 2024 · The FOREIGN KEY creates a relationship between the columns in the current table or let’s say table A (the one with the foreign key) and the referenced table or table B (the one with the unique key).
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.
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.
