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8 lut 2021 · ON DELETE CASCADE constraint is used in MySQL to delete the rows from the child table automatically, when the rows from the parent table are deleted. For example when a student registers in an online learning platform, then all the details of the student are recorded with their unique number/id.
- Production Databases in SQL Queries
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- Production Databases in SQL Queries
The DELETE statement is used to delete existing records in a table. DELETE Syntax. DELETE FROM table_name WHERE condition; Note: Be careful when deleting records in a table! Notice the . WHERE clause in the DELETE statement. The WHERE clause specifies which record (s) should be deleted.
This tutorial shows you how to use MySQL ON DELETE CASCADE to automatically delete data from a child table when you delete data from the parent table.
4 lut 2009 · You have to define your Foreign Key constraints as ON DELETE CASCADE. Note: You need to use InnoDB storage engine, the default MyISAM storage engine not support foreign keys relation.
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.
20 cze 2013 · ON DELETE CASCADE: if a row of the referenced table is deleted, then all matching rows in the referencing table are deleted. ON DELETE SET NULL: if a row of the referenced table is deleted, then all referencing columns in all matching rows of the referencing table to be set to null.
The MySQL ON DELETE CASCADE constraint ensures that when a row in the parent table is deleted, all related rows in the child table are automatically deleted as well. This constraint helps maintain referential integrity between two tables that are connected through a foreign key relationship.
