What is Cascade delete rule?

A foreign key with cascade delete means that if a record in the parent table is deleted, then the corresponding records in the child table will automatically be deleted. This is called a cascade delete in SQL Server.

What is onDelete (‘ cascade ‘) in laravel?

onDelete(‘cascade’); simply adds ON DELETE CASCADE rule to your database which specifies that the child data gets deleted when the parent data is deleted. Note: take care of the typo (double semicolon) $table->foreign(‘user_id’)->references(‘id’)->on(‘users’)->onDelete(‘cascade’);

What is on delete cascade example?

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.

Is on delete cascade good practice?

On delete cascade is a particularly bad thing to use to clean data because it doesn’t discriminate against the data you want the FK to stop the delete for and the data you are trying to completely purge.

How do you write on delete cascade in SQL?

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 Cascade constraints in SQL?

CASCADE CONSTRAINTS. Specify CASCADE CONSTRAINTS to drop all referential integrity constraints that refer to primary and unique keys in the dropped table. If you omit this clause, and such referential integrity constraints exist, then the database returns an error and does not drop the table.

How do I use cascade delete in SQL?

What is delete delete and null Cascade?

ON DELETE CASCADE : SQL Server deletes the rows in the child table that is corresponding to the row deleted from the parent table. ON DELETE SET NULL : SQL Server sets the rows in the child table to NULL if the corresponding rows in the parent table are deleted.

Where do I put the delete cascade?

What is Cascade constraints?

CASCADE CONSTRAINTS. Specify CASCADE CONSTRAINTS if you want to drop all foreign key constraints that refer to the primary and unique keys defined on the dropped columns as well as all multicolumn constraints defined on the dropped columns.