???? Role of default database and default table in SQL Server

We know that the Oracle Database installation architecture can be 1 databases corresponding to 1 or more instances. In SQL Server, the schema is the exact opposite of Oracle, which is 1 instances (the default instance named hostname hostname) contains multiple databases, in the SQL Server database (2000,2005,2008, etc.), and mainly contains 4 default databases. The master database, model database, tempdb database, and msdb database , respectively. These databases are the heart and soul of SQL Server. In addition, two instance databases are installed by default: TheNorthwind database and the pubs database.

System Database

master database	The master database controls all aspects of SQL Server. This database includes all configuration information, user logon information, and information about the process that is currently running on the server.
Model database	The model database is the template that is created for all user databases. When you create a new database, SQL Server creates a copy of all the objects in the model database and moves it to the new database. After the template object is copied to the new user database, all the extra space for the database is filled with empty pages.
tempdb database	The tempdb database is a very special database that is used by all users who access your SQL Server. This library is used to hold all temporary tables, stored procedures, and other temporary objects created by SQL Server. For example, the tempdb database is used for sorting. The data is put into the tempdb database, and the results are returned to the user after the sequence is completed. Every time SQL Server restarts, it empties the tempdb database and rebuilds it. Never create a table that needs to be persisted in the tempdb database
msdb database	The msdb database is a special case in SQL Server. If you look at the actual definition of this database, you will find that it is actually a user database. The difference is what SQL Server does with this database. All task schedules, alarms, and operators are stored in the msdb database. Another function of the library is to store all the backup history. The SQL Server Agent will use this library.

Sample Database

Northwind sample Database	The Northwind Traders sample database contains sales data for a fictitious company named Northwind Traders, which engages in the import and export trade of specialty foods from around the world
The Pubs sample Database	The pubs sample database is modeled on a book publishing company and is used to demonstrate Microsoft? SQL Server? Many of the options available in the database. The database and the tables in it are often used in the examples described in document content.

The role of default tables in SQL Server creation in databases

name	Address	Description
Sysaltfiles	Primary database	Save the file for the database
Syscharsets	Primary database	Character Set and sort order
Sysconfigures	Primary database	Configuration options
Syscurconfigs	Primary database	Current configuration options
sysdatabases	Primary database	Databases in the server
Syslanguages	Primary database	Language
syslogins	Primary database	Login account Information
Sysoledbusers	Primary database	Link Server login Information
sysprocesses	Primary database	Process
Sysremotelogins	Primary database	Telnet account
syscolumns	Each database	Column
Sysconstrains	Each database	Limit
Sysfilegroups	Each database	File groups
Sysfiles	Each database	File
Sysforeignkeys	Each database	External keywords
sysindexes	Each database	Index
Sysmenbers	Each database	Role members
sysobjects	Each database	All database objects
Syspermissions	Each database	Permissions
Systypes	Each database	User-defined data types
sysusers	Each database	User

???? Role of default database and default table in SQL Server