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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.
Add Foreign Key using ALTER TABLE. The following SQL command adds a Foreign Key to an existing table. ALTER TABLE Subject ADD FOREIGN KEY (StudentID) REFERENCES Student(StudentID); Drop foreign key MySQL. For dropping a Foreign key from a MySQL table, you need to know the name of the foreign key first.
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
5.6.6 Using Foreign Keys. 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 ...
1 sie 2010 · MySQL Workbench enables you to add a foreign key from within the table editor or from within an EER diagram by using the relationship tools on the vertical toolbar. This section describes how to add a foreign key using the foreign key tools.
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. ADD CONSTRAINT FK_PersonOrder.
You can add a foreign key constraint to an existing table using the following ALTER TABLE syntax: ALTER TABLE tbl_name ADD [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (col_name, ...) REFERENCES tbl_name (col_name,...) [ON DELETE reference_option] [ON UPDATE reference_option]
