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one, key and primary key differenceint (one) not NULL auto_increment, user_name varchar (defaultDefault NULL, logrecord_operation varchar (defaultAnalytical:KEY Wh_logrecord_user_name (USER_NAME)The User_name field in this table establishes a foreign key with the Wh_logrecord_user_name table user_name fieldOutside the parentheses is the table that establishes th

Key:I understand the public key + private key collectively. Key pair:The Public key (certificate) and private key are in pairs.Each side of the communication holds its own private key and the other's public

Reprint: http://blog.csdn.net/a1232345/article/details/44594867 explanation of public key and private key公钥: For outward release, accessible to anyone,私钥: To save yourself, do not give othersThe two situations are often confused and must be understood.Case 1: Public key for "encryption", private key for "decryption"If

http://www.btcside.com/new/detail/2145 This is the three words that often appear in Bitcoin, so what do they mean by each other? What kind of relationship do they have? Let's talk about a private key, such as a string 5KYZDUEO39Z3FPRTUX2QBBWGNNP5ZTD7YYR2SC1J299SBCNWJSS, which is a private key. Any application that correctly supports the Bitcoin protocol can recognize the string as a private

Label:First, what is the primary key, foreign key: There are several attributes in a record in a relational database, which can be a primary key if one of the attribute groups (note is a group) uniquely identifies a record: Student Table (School number, name, gender, Class) Each student's school number is unique, the study number is a primary

This article is referenced from:http://blog.csdn.net/bingqingsuimeng/article/details/51595560First, what is the primary key, foreign key:There are several attributes in a record in a relational database, which can be a primary key if one of the attribute groups (note is a group) uniquely identifies a record.Like whatStudent Table (School number, name, gender, Class)Each student's school number is unique, th

Tags: primary key first break range Ror add comment art DropSQL PRIMARY KEY ConstraintThe PRIMARY KEY constraint uniquely identifies each record in a database table. The primary key must contain a unique value. Primary key columns cannot contain NULL values. Each table shoul

login information and become a basic solution for Internet security, which has become a standard configuration for Linux systems.It should be noted that SSH is only a protocol, there are many implementations, both commercial and open source implementation. The implementation of this article is OpenSSH, it is free software, the application is very extensive.Encrypting all transmitted data so that the "man-in-the-middle" attack is not possible, and it can prevent DNS and IP spoofing, which is SSH

First, what is primary key, foreign key:A record in a relational database has several properties, and if one of the attribute groups (note the group) uniquely identifies a record, the attribute group can be a primary key such as: Student form (school number, name, gender, Class) Each student's number is unique, and the number is a primary key. User table (user

Des:Digital Encryption Standard. Obsolete Standard.Single key algorithm is the sender of the information using key A for data encryption, the receiver of the information uses the same key a for data decryption. The single key algorithm is a symmetric algorithm.The algorithm is good at adding/solving speed, the

1. Definition 1.1 What are primary keys and foreign keys 1.2 The role of primary and foreign keys 1.3 Differences between primary key, foreign key, and index 2. Primary key (primary key) 2.1 Setting the primary key via SSMs 2.2 Setting prim

The ORA exception was encountered today when a unique index was established on an existing table Ora-02437:cannot Validate (primary KEY or UNIQUE key constraint name)-PRIMARY key violated The data for a primary key or unique key has a duplicate value, typically an error in

Primary key repeat duplicate entry ' xxx ' for key ' PRIMARY ' when MySQL primary key is set to Auto_increment, concurrency performance test occursWorkaround:Add settings to the [mysqld] fragment in My.cnf innodb_autoinc_lock_mode=0Also pay attention to increasing the number of active links in JDBC, such as setting jdbc.maxactive=300, because setting innodb_autoi

Bob,alice and digital certificates The most well-known characters in network security are probably Bob and Alice, because many of the security principles are illustrated with these two virtual characters. Let's see how Bob gets a digital certificate from the CA Center: 1, Bob first creates his own key pair (key pair), including the public key and private

The definition of a primary key: A collection of columns or columns that is used to uniquely identify a row in a table. Only one primary key is allowed on a table.When we specify a primary key in the database, it is defined by a PRIMARY key constraint. When you create a PRIMARY key