create unique id

This article mainly describes how to generate globally unique IDs in a distributed system. Preface Simply generating global IDs is not a challenge, generating a global unique ID to meet the following requirements: Ensure that the generated ID is

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

What is the difference between the unique key constraint of SQLServer and the unique index ?, Sqlserver Index I used to want to know what the difference was, but I forgot it because we seldom use the unique key constraint. A few days ago, my

Generally, we can see that the terms "Index" and "key" are used for exchange, but they are actually different. An index is a physical structure stored in a database. A key is purely a logical concept. The key represents the integrity constraints

I used to want to know what the difference was, but it was forgotten because we seldom used a unique key constraint. It was not until a few days ago that my colleague gave me a script to constrain the uniqueness of a field with a unique key

There are a number of scenarios and requirements that you need to use a unique identifier for your mobile device.In Android, there are several ways to get such an ID.1. The IMEI: only valid for Android phones: 12

Http://www.cnblogs.com/lsx1993/p/4663125.html "Database primary key scheme in distributed environment" [Http://www.2cto.com/database/201309/243195.html] Using a self-added primary key ID is certainly the best fit when using only a single database.

Background: During this time, I will create some website programs for a tourism website. The data table is roughly as follows: the general situation of the database table is the Access database. There are two data tables: TC_TourCompany and

 1. Description of unique constraints on the official website Http://download.oracle.com/docs/cd/E11882_01/server.112/e16508/datainte.htm#CNCPT1642   Uniquekey constraint requires that every value in a column or set of columns beunique. no rows of a

In the development process, we usually use auto-increment numbers as the id primary key for data tables, and id is a numeric type, which is not easy to understand. After converting IDs into numbers in a certain format, it is easy to know what the