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2 sty 2013 · Mysql has a special syntax for dropping foreign key constraints: ALTER TABLE tbl_magazine_issue DROP FOREIGN KEY FK_tbl_magazine_issue_mst_users
The DROP CONSTRAINT command is used to delete a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint. DROP a UNIQUE Constraint. To drop a UNIQUE constraint, use the following SQL: SQL Server / Oracle / MS Access: ALTER TABLE Persons DROP CONSTRAINT UC_Person; MySQL: ALTER TABLE Persons DROP INDEX UC_Person; DROP a PRIMARY KEY Constraint.
6 lut 2024 · The SQL syntax to drop a FOREIGN KEY constraint is: ALTER TABLE child_table_name DROP FOREIGN KEY constraint_name; Replace ‘child_table_name’ with the name of the table from which you want to remove the constraint and ‘constraint_name’ with the name of the FOREIGN KEY constraint.
Summary: in this tutorial, you will learn about the MySQL Foreign Key constraint and how to create, drop and disable a foreign key constraint. MySQL Foreign Key Introduction. A foreign key is a column (or set of columns) that establishes a relationship between data in two tables.
To delete a foreign key from a table, use the ALTER TABLE clause with the name of the table (in our example, student) followed by the clause DROP CONSTRAINT with the name of the foreign key constraint.
If you want to disable a foreign key constraint from a specific table, you can use the following syntax. ALTER TABLE table_name DISABLE KEYS; After completion of the specific work on the table, you can re-enable the Foreign key constraint by the following statement.
MySQL FOREIGN KEY Constraint. The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in another table.
