MySQL DELETE CASCADE

ON DELETE CASCADE clause in MySQL is used to automatically remove the matching records from the child table when we delete the rows from the parent table. It is a kind of referential action related to the foreign key.

1. How do I delete cascade?
2. What is the functions of an delete cascade?
3. Where can I use delete cascade?
4. What is on delete cascade and on Delete Set Default?
5. How do I change the table on delete cascade?
6. What is the difference between on delete set null and on delete cascade?
7. What is the function of on Delete?
8. Which of the following is used to delete an entire MySQL database?
9. What is on update cascade in MySQL?

How do I delete cascade?

Edit table and columns specification by clicking … as shown in the below image.

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

What is the functions of an delete cascade?

What is the functions of on delete cascade? b) It is used to specify the precise attribute that needs to be deleted in a single relation. d) It is used to execute sub-queries in the from clause. Explanation: It is used to preserve referential integrity in the relation.

Where can I use delete cascade?

Use the ON DELETE CASCADE option if you want rows deleted from the child table when the DELETE or MERGE statement removes corresponding rows from the parent table.

What is on delete cascade and on Delete Set Default?

It means that the child data is set to NULL when the parent data is deleted or updated. SET DEFAULT. It is used in conjunction with ON DELETE or ON UPDATE. It means that the child data is set to their default values when the parent data is deleted or updated.

How do I change the table on delete cascade?

Alter table to remove Foreign Key or add DELETE CASCADE (MySQL)

1. Step 1 : Get the Foreign Key Name.
2. Step 2: Drop the Foreign Key.
3. Step 3: Now add the foreign key constraint back again, this time with ON DELETE CASCADE.

What is the difference between on delete set null and on delete cascade?

CASCADE : Delete or update the row from the parent table and automatically delete or update the matching rows in the child table. Both ON DELETE CASCADE and ON UPDATE CASCADE are supported. ... SET NULL : Delete or update the row from the parent table and set the foreign key column or columns in the child table to NULL .

What is the function of on Delete?

The delete key is a key on most computer keyboards which is typically used to delete either (in text mode) the character ahead of or beneath the cursor, or (in GUI mode) the currently-selected object. The key is sometimes referred to as the "forward delete" key.

Which of the following is used to delete an entire MySQL database?

Explanation: The 'TRUNCATE' keyword in MySQL is used to delete all the rows from the table and also free the space containing the table. Its syntax is: TRUNCATE TABLE my_table.

What is on update cascade in MySQL?

So, for example, adding the ON UPDATE CASCADE clause to a foreign key definition tells MySQL that when a record is updated in the primary table (the table referenced for foreign key checks), all records using that foreign key value in the current table should also be automatically updated with the new values to ensure ...