## Part 1: Overview of Database
* 1, * Basic Concepts
- Data: data descriptor record things. (Basic objects stored in the database)
- a database (DB): Data stored on a computer to store a certain format.
- Database Data Features: permanently stored, organized, can be shared.
- database management system (DBMS): designed to implement data management and system software maintenance.
- Database Systems (DBS): by the database, the database management system (core), applications, database administrator components.
* 2, * data independence
- Logical Independence: When content changes in the expression of the real world, does not affect the characteristics of the application.
- physical independence: when the storage location and the data storage structure is changed, does not affect the characteristics of the application.
* 3, * shortcomings manage files
- does not provide data sharing
- data redundancy is inevitable
- the lack of security
- is not conducive to maintaining consistency of data
- applications and file structure is tightly coupled
## Part 2: Database System Structure
* 1, * data characteristics
- static features: including the basic structure of the data, the link between the data and the constraints on the range of data
- dynamic feature: operate on the data that matches certain criteria, data query and change data
* 2, the basic concept *
- three elements data model: the basic structure of the data, constraint condition data, defined operation on the data (this is a dynamic characteristic)
- data model: organization of data
- data model classification (depending on the purpose of the model application) : conceptual data model layer, tissue layer data model
* 3, * conceptual data model layer
Yet conceptual data model layer conceptual model / model information, from the perspective of semantic data model to extract the application and press a user point to model the data and information.
It is the first abstraction of the real world to the world of information: the conceptual data model is a layer of abstraction of the real world, forming the world's information model.
Entity - Relationship model (ER FIG)
entities Contact: Contact-one (1: 1), many relationship (1: n-), contact-many (m: n)
* 4, * organizational hierarchy data model
Also known as tissue layer tissue model data model, data is organized according to a database will be described.
The second layer is an abstraction of the real world information: tissue layer data model is to abstract faith community and conversion, data organization model of the formation of a specific DBMS supports.
Four models: hierarchical model, the mesh model, ** ** relational model, object-oriented model
relational schema: relationship name (attribute 1, attribute 2)
5, the relational model data integrity constraints
entity integrity, with reference to intact, intact user-defined
6, the mode structure of the database system
- the mode (storage mode): physical data storage, only one, not a relationship of
- an outer mode (user mode or sub-mode): Data View, internal representation, the display data, a plurality
- conceptual schema (logical mode or modes): contains all the data, it must be a relationship. It is a description of all the logical data structures and database features.
External mode / image mode, mode / the pattern image
7, DBMS function
data definition, data manipulation, and performs optimization, security and data integrity, data recovery, and concurrency, data dictionary, the performance
## Part 3：SQL
* 1, SQL language functions and features *
functions: data definition, data query, data manipulation, data control
Features: integrated, highly automated, simple, can be used in a variety of ways
* 2, data integrity type *
- Data integrity refers to the correctness and compatibility of data
- entity integrity, referential integrity, the user-defined intact
* 3, * View
View is a logical window of data selected out of the base table in the database consisting of a combination of part of the basic table rows and columns of data.
* 4, * view of the benefits
- to simplify data query
- allows the user to look at the same data from multiple perspectives
- to improve the security of data
- it provides a degree of independence logic
* 5, * relational schema
- dependent: all rely, in part dependent
- Scaling: candidate code, the primary code, full code, outer code, the main property, non-primary property
* 6, * paradigm (of NF)
- The first paradigm: not contain repeating groups
- second paradigm: the paradigm is based on the first, non-primary attributes are fully dependent on the primary code
- third paradigm: the second paradigm based on the non-primary property is not dependent on the primary code transmitted
## Part 4: protection of databases
* 1, * Basic Concepts
- transaction: User defined data manipulation series
- wherein the transaction (ACID characteristics): atomicity, consistency, isolation, durability
- transaction database concurrency control and recovery of the basic unit
* 2, SQL * transaction model
two kinds of transactions: Transaction display, implicit transaction
show two transaction transaction model: ISO transaction model, T-SQL transaction model
* 3, data inconsistency caused by concurrent operation *
- Modify loss of data
- read "dirty" data
- non-repeatable read
- produce a "ghost" Data
* 4, concurrency control measures *
- Shared locks: shared locks on the basis of a shared lock can be combined with
- exclusive lock: With exclusive lock can not add any locks
* 5, three locking protocol *
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* 6, * serializable schedule
for all transactions executed concurrently comply with two-phase locking protocol
two-phase locking protocol: everything must be carried out in two phases to lock and unlock data
* 7, * database failure
within a transaction failures, system failures, other failures
* 8, * database backup and restore
the full backup, differential backup, log backup
## ** Part 5: Database Design **
* 1, * the basic steps of database design
requirements analysis, design, behavior design, database implementation, database operation and maintenance phase
- needs analysis: top-down, stepwise decomposition
- Design: conceptual design, logical structure design, physical structure design
- Design Concept: the ER Model
* 2, * composition database
- two types of databases: Database system, a user database
- consisting of two files: a data file (.mdf primary secondary .ndf), the log file (.ldf)
## Part 6: Data Query function statement
The SELECT * | <column name> | computed columns | constants are listed | count (*) | count ( distinct < column name>) | SUM (column name) | AVG (column name) | MAX (column name) | top n | top n percent | distinct
The FROM <table name> | <table 1, table 2, table name n> | the Join Table 1 Table 2 ON | Table 2 Table 1 left join ON
|WHERE =,>,!=|in()|between and|is null|>(),=()|and,or|like
|GROUP BY
|HAVING
|ORDER BY asc|desc
|UNION | INTERSECT | EXCEPT
## Part 7: definition and data manipulation function clauses
Custom Functions
创建：CREATE TABLE <表名>(创建语句)
删除：DROP TABLE <表名1,表名2,表名N>
更新：ALTER TABLE <表名>
ALTER COLUMN <列名> <类型>
|DROP COLUMN <列名>
|ADD <列名> <类型> <约束>Manipulation functions
插入：INSERT <表名>(列名) VALUES(值)
删除：DELETE <表名>
更新：UPDATE <表名> SET <列名>=值