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To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY constraint on multiple columns, use the following SQL syntax: ALTER TABLE Orders ADD CONSTRAINT FK_PersonOrder
ALTER TABLE child_table_name ADD FOREIGN KEY (child_table_column) REFERENCES parent_table_name(parent_table_column); child_table_name is that table in which we want to add constraint. child_table_column is that table column in which we want to add foreign key.
8 kwi 2021 · Syntax –. ALTER TABLE table_name ADD FOREIGN KEY (column_name) REFERENCE table_name (Referencing column_name in table_name); Query –. ALTER TABLE exam ADD FOREIGN KEY (student_id) REFERENCES student (student_id);
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, ...) REFERENCES tbl_name (col_name,...) [ON DELETE reference_option] [ON UPDATE reference_option] reference_option:
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: ALTER TABLE Orders
MySQL supports ON UPDATE and ON DELETE foreign key references in CREATE TABLE and ALTER TABLE statements. The available referential actions are RESTRICT , CASCADE , SET NULL , and NO ACTION (the default).
The foreign key on the column reportTo is known as a recursive or self-referencing foreign key. 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, ...)
