database foreign key tutorial

This article mainly introduces the specific definition and usefulness of super-key, candidate key, primary key, main attribute, foreign key in MySQL database. You can also refer to the topic.alibabacloud.com MySQL video tutorial and MySQL

primary KEY (Primary key) each of the data in the table is a unique value in the form. Other words. It is used to uniquely identify each row of data in a table.The primary key can be a field within the original data. Or a man-made field (a field

primary KEY (Primary key) each of the data in the table is a unique value in the form. In other words, it is a unique way to identify each row of data in a table. The primary key can be a field in the original data, or a man-made field (a field that

Simple tutorial on SQL statements in linux --- primary key, foreign key, and SQL Primary Key)Each item in is a unique value in the table. In other words, it is used to uniquely identify each row of data in a table. A primary key can be a column in

primary KEY (Primary key) each of the data in the table is a unique value in the form. In other words, it is a unique way to identify each row of data in a table. The primary key can be a field in the original data, or a man-made field (a field that

myeclipse Database Tutorial: How to use tables, foreign keys, and indexesMyEclipse's Database Explorer tool provides a number of wizards and actions to easily create and delete tables, relationships, and indexes. In this tutorial, you will learn to:

In-depth explanation of mysql foreign key association issues BitsCN.com continues to read the book "mysql database development" recommended by the instructor. I encountered a problem when I saw the foreign key association problem with the innodb

· What is a database?The warehouse where the data is stored.· What is the difference between a database and a data structure?To solve the problem of manipulating data in memory, the database should solve the problem of manipulating data in the hard

Failed to add MySQL foreign key ERROR1452 BitsCN.com An ERROR 1452 ERROR occurred while adding foreign keys to MySQL. today, when I learned how to add foreign keys to the database, I first created two tables orders and order_items. the storage

This error occurs because the MySQL tutorial has always been unable to support the problem of relationships, unfortunately, it does not indicate which problem is causing the above error, and I list the common causes of this terrible 150 error, and I