cascading operations for MySQL

1. CREATE Table A

CREATE Table A (

Name char (not NULL),

ID char (NOT NULL primary key);

2. CREATE TABLE B

CREATE TABLE B (

B_name char (not NULL),

b_id char (not NULL),

Constraint foreign KEY (b_id) references a (ID) on DELETE cascade);

3. After the table is built, insert the data

Insert into a values ("111", "1");

Insert into a values ("222", "2");

Insert the following data into B values ("1", "1") in table B Display insert succeeded.

Insert the following data into B values ("1", "3") in table B Show Insert failed. This is because the foreign key is set and the ID in table A is not (id== "3") data.

Execute delete from a where id= "1"; The data in table B will also be deleted. The cascading deletion is applied here.