SQL Server Overview

The objects contained in SQL Server:

databases , transaction logs , indexes , filegroups , database diagrams , views , stored procedures , user- defined functions , users , roles , assemblies , tables , reports , full-text Catalogs , user-defined data types

The database is actually the highest-level object, and all other objects are child objects

1. The system databases included in the installed SQL Server:

Master database holds a special set of tables (system tables) for the overall control of the system (not deleted)

The model database is a database of models that can be modeled as a new database (not deleted)

msdb is where the SQLAgent process stores any system tasks, such as scheduling a daily backup of the database

Tempdb is one of the main working areas of the server, and when you perform some complex or large query tasks, you need to create an intermediate table to complete, and this table is created in tempdb

2. Transaction log

Http://www.cnblogs.com/CareySon/archive/2012/02/13/2349751.html

What is a thing log?

 1) transaction log file transaction The log file is a file used to record database updates, with an LDF extension of 
 2) that SQL Server uses transaction logs to ensure persistence (durability) and transaction rollback (Rollback). 
 
     
 
 3. What is an index? The 
 Index is the list of data in the data table and the corresponding storage location, and using an index can improve the speed of finding data in a table or view. 
 Indexes: Clustered and nonclustered indexes  

< p> Clustered index	Nonclustered index
Each table only allows Create a clustered index	can have up to 249 nonclustered indexes
The data in the physical rearrangement table is in compliance with index constraints	Creates a list of key values that point to the location of the data in the data page
Columns used to find data frequently	columns for finding a single value from a table

4. Triggers
What is a trigger?
a trigger is a piece of code that executes automatically when a table operation (insert, delete) is performed , primarily for copying data at input or updating to check the data to ensure that the data meets the appropriate standards

5, constraint
Data integrity refers to the correctness and consistency of the data, which can be defined by defining the integrity constraints, or through rules, indexes, triggers, and so on.
In simple terms, the restrictions on each column or table
Constraint type: Uniqueness and PRIMARY KEY constraint, FOREIGN KEY constraint, check constraint, NULL constraint, default value constraint,

I'll say something else.

SQL Server Overview