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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]
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.
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] [ON UPDATE reference_option] Code language: SQL (Structured Query Language) (sql)
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.
Foreign keys let you cross-reference related data across tables, and foreign key constraints help keep this spread-out data consistent. MySQL supports ON UPDATE and ON DELETE foreign key references in CREATE TABLE and ALTER TABLE statements.
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).
