mysql primary key two columns

Key differs from primary keyKey is usually the index synonym. If the keyword attribute primary key is given in the column definition, then primary key can also be specified as key only. The purpose of this is to be compatible with other database

Reprinted from: http://blog.csdn.net/sunrise918/article/details/5575054These days on the logical primary key, business primary key and composite primary key have some thinking, also searched the related discussion on the net, related discussion can

Reproduced: http://blog.csdn.net/sunrise918/article/details/5575054 In the past few days, I have thought about logical primary keys, business primary keys, and composite primary keys. I also searched for some discussions on the Internet. For more

Mysql auto-incrementing column leads to duplicate primary key issue analysis..., mysql primary key A few days ago, the development of shoes reported a problem of using the load data infile command to import data primary key conflicts. After analysis,

Concept:A primary key (primary key) uniquely identifies a property or group of properties for a row in a table. A table can have only one primary key, but there may be multiple candidate indexes. Primary keys often form referential integrity

What are the differences among KEY, primary key, unique key, and INDEX in MySQL? mysqlunique You can split the questions raised in the questions to solve them step by step. In MySQL, KEY and INDEX are synonymous. This problem can be simplified to

I. What is an index?Indexes are used to quickly look for records with specific values, and all MySQL indexes are saved as B-trees. If there is no index, MySQL must start scanning all records of the entire table from the first record until it finds a

Transferred from: http://blog.csdn.net/duck_arrow/article/details/8264686Concept:A primary key (primary key) uniquely identifies a property or group of properties for a row in a table. A table can have only one primary key, but there may be multiple

Set MySQL data table primary key: Use the "PRIMARY key" keyword to create a primary key data column. The primary key column is set to not allow duplicate values, in many cases combined with "auto_increment" incrementing numbers. As shown in the

Original: MySQL primary key design[TOC]In the process of the project encountered a seemingly very basic problem, but in-depth thinking has led to a lot of problems, I think it is necessary to take this learning process to record.MySQL primary key