Can we delete a row with foreign key?

Suppose there is a main table containing a primary key and there is another table which contains a foreign key to this main table. So if we delete the row of main table it will delete the child table also.

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Can we delete a table with foreign key?

You can delete a foreign key constraint in SQL Server by using SQL Server Management Studio or Transact-SQL. Deleting a foreign key constraint removes the requirement to enforce referential integrity.

What happens to foreign key when primary key is deleted?

When a referenced foreign key is deleted or updated, respectively, the columns of all rows referencing that key will be set to NULL . The column must allow NULL or this update will fail.

How do I delete a foreign key constraint in MySQL?

You can drop a foreign key constraint using the following ALTER TABLE syntax: ALTER TABLE tbl_name DROP FOREIGN KEY fk_symbol; If the FOREIGN KEY clause defined a CONSTRAINT name when you created the constraint, you can refer to that name to drop the foreign key constraint.

How do I delete a row in a trigger?

Here is the basic syntax of creating a MySQL BEFORE DELETE trigger:

CREATE TRIGGER trigger_name BEFORE DELETE ON table_name FOR EACH ROW trigger_body.
DELIMITER $$ CREATE TRIGGER trigger_name BEFORE DELETE ON table_name FOR EACH ROW BEGIN — statements END$$ DELIMITER ;

Can we delete foreign key without deleting primary key?

To successfully change or delete a row in a foreign key constraint, you must first either delete the foreign key data in the foreign key table or change the foreign key data in the foreign key table, which links the foreign key to different primary key data.

How do I delete a foreign key constraint in SQL Server?

Creating a foreign key with DELETE and UPDATE CASCADE rules

Select the parent table and the primary key column in the parent table.
In the INSERT and UPDATE specifications, select Cascade for the delete rule.
Click on Close and save the table in the designer.

How do I delete a foreign key in SQL Workbench?

To drop a foreign key, right-click the row you wish to delete, then select the Delete Selected FKs menu item. To modify properties of a foreign key, select it and make the desired changes.

How do I create a trigger for delete?

The following is the syntax to create a BEFORE DELETE trigger in MySQL:

CREATE TRIGGER trigger_name.
BEFORE DELETE.
ON table_name FOR EACH ROW.
Trigger_body ;

What is Cascade delete in SQL?

Use the ON DELETE CASCADE option to specify whether you want rows deleted in a child table when corresponding rows are deleted in the parent table. If you do not specify cascading deletes, the default behavior of the database server prevents you from deleting data in a table if other tables reference it.

What happens when a foreign key is updated?

No the foreign key is not updated automatically. You need to update the foreign key in the tables in which it is referenced by yourself else it would result in referential integrity exception. For updating the foreign key automatically you may use TRIGGERS.

How do I use delete cascade in SQL?

How do you drop a foreign key?

Dropping foreign keys

To drop foreign keys using the Control Center: Expand the object tree until you see the Tables folder. Right-click the table you want to modify, and select Alter from the pop-up menu.
To drop foreign keys using the command line, enter: ALTER TABLE name DROP FOREIGN KEY foreign_key_name.

How do you create a trigger to delete in SQL?

To delete a DML trigger

In Object Explorer, connect to an instance of Database Engine and then expand that instance.
Expand the database that you want, expand Tables, and then expand the table that contains the trigger that you want to delete.
Expand Triggers, right-click the trigger to delete, and then click Delete.

How do you create a trigger delete in SQL Server?

To delete a DML trigger In Object Explorer, connect to an instance of Database Engine and then expand that instance. Expand the database that you want, expand Tables, and then expand the table that contains the trigger that you want to delete. Expand Triggers, right-click the trigger to delete, and then click Delete.