现在,我们可以向Customers表和Orders表中插入一些数据,以验证外键的效果。 -- 插入顾客数据INSERTINTOCustomers(customer_id,customer_name,customer_email)VALUES(1,'John Doe','john.doe@example.com');-- 插入订单数据INSERTINTOOrders(order_id,order_date,customer_id)VALUES(1,'2022-01-01',1); 1. 2. ...
1 mysql使用foreign key 设置外键,php中也可以使用命令来这样做语句是create table example3(id int,stu_id int,course_id int,constraint stu_f foreign key(stu_id,corse_id) references example2(stu_id,course_id)); 即可其中 constraint stu_f foreign key(stu_id,corse_id) references example2(stu_...
This following example relates parent and child tables through a single-column foreign key and shows how a foreign key constraint enforces referential integrity. Create the parent and child tables using the following SQL statements: CREATE TABLE parent ( id INT NOT NULL, PRIMARY KEY (id) ) ...
FOREIGN KEY foreign_key_name(columns) REFERENCES parent_table(columns) ON DELETE action ON UPDATE action; MySQL adding foreign key example# Now, let’s add a new table named vendors and change the products table to include the vendor id field: 1 2 3 4 5 6 7 8 9 USE dbdemo; CREATE...
AS AN EXAMPLE, 3 TABLES THAT I HAVE ARE: 1.)LOGIN 2.)USER 3.)AREAS IN THE LOGIN TABLE I HAVE THE COLUMNS: TID,LOGIN_NAME,PASSWORD(PRIMARY KEY TID) IN THE USER TABLE I HAVE: TID,FIRSTNAME,LASTNAME,SEX(PRIMARY KEY TID) IN THE AREAS TABLE I HAVE: TID,AREAS(PRIMARY...
You can obtain information about foreign keys from the Information SchemaKEY_COLUMN_USAGEtable. An example of a query against this table is shown here: mysql>SELECTTABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAMEFROMINFORMATION_SCHEMA.KEY_COLUMN_USAGEWHEREREFERENCED_TABLE_SCHEMAISNOTNULL;+---+-...
MySQL creating table foreign key example The following example creates a dbdemo database and two tables: categories and products. Each category has one or more products and each product belongs to only one category. The cat_id field ...
MySQL foreign keys and ON UPDATE and ON DELETE MySQL foreign keyFAQ: How do I define a foreign key in MySQL? Answer: Here's a quick example of how I typically define a foreign key in MySQL. Diving right into an example, here's the definition for a MySQL database table namednodesthat...
Foreign Key Constraint Examples This simple example relatesparentandchildtables through a single-column foreign key: CREATE TABLE parent ( id INT NOT NULL, PRIMARY KEY (id) ) ENGINE=INNODB; CREATE TABLE child ( id INT, parent_id INT,
my problem is that after creating a foreign key, I cannot see in MySQL/phpMyAdmin that a column is a foreign key, here is an example of 2 tables (I wanted to create a table with users in a community an create a table=relationship which contains the information about which users know ea...