01 Basic Theory of relational database

A method of data processing

File System Management methods:

Data redundancy

Data access difficulties

Data isolation

Consistency, security, integrity not guaranteed

Atomicity issues

Concurrent Access Exceptions

Two documents

Presentation Layer

File

Logical layer

File system: Storage Engine

Physical Layer

Meta data

Data: Data blocks

relational database

Presentation layer: Table

Logical layer: Storage engine

Physical Layer: Data file

Three-relationship model

Relational model

Entity-Relationship Model

Object Relational Model

Semi-structured data model: XML (extended Memento language)

Quad SQL

System R:sql The world's first relational database

Constraint constraint

Domain constraints: Data type constraints

FOREIGN KEY constraints: referential integrity constraints

PRIMARY KEY constraint: A field can uniquely identify the entity to which this field belongs, and cannot be empty, only one primary key in a table

Candidate Key:

Uniqueness constraint: A field in each row is not allowed to have the same value, can be empty, a table can have more than one

Check constraint: Age:int

Five data storage and querying

Storage Manager

Permissions and integrity Manager

Things Manager

File Manager

Buffer Manager

Query Manager

DML Interpreter

DDL interpreter

Query execution engine

Single-process multi-threading, daemon thread, application thread

Relational operations:

Projection: Output only the specified attribute column

Select: Output only the specified record line

Natural joins: Rows with the same value on all property values with the same name

Cartesian product;

and the set operation.

SQL query statement:

Ddl

Dml

DCL

How to interact with RDBMS using the programming language:

Embedded SQL, similar to dynamic SQL, but whose language must be fully determined when compiling in ascending order (0DBC)

Dynamic SQL: The programming language uses the function (mysql_connect ()) method to establish a connection with the RDBMS server and interact with the SQL Server by establishing a connection to send a query statement and save the result to a variable and backward Row processing (JDBC)

MySQL plug-in storage engine

5.5.8 before: Myisam does not support transactions for more than the query, modified less scenes, especially for the application Data Warehouse

After 5.5.8: InnoDB support transaction for online transaction processing

01 Basic Theory of relational database