MySQL series one relational database theory

Basic theory of mysql-relational database

Relational model: (Structured data model)

Relational model

Entity-Relationship Model

Object Relational Model: an object-based data model

Semi-structured data model

Relationships: Relational algebra operations

Intersection:

and set:

Subtraction

Complete:

Complement set:

SQL: Structured Query Language

DML: Data Manipulation language

Insert

Delete

Select

Update

DDL: Data Definition language

Create

Drop

Alter

DCL: Data Control Language

Grant

Revoke

relational database

Presentation layer: Table

Logical layer: Storage engine

Physical Layer: Data file

Data storage and querying

Storage Manager

Permissions and Integrity Manager:

Transaction manager:

File Manager:

Buffer Manager:

Query Manager

DML Interpreter

DDL interpreter

Query execution engine

Relational operations:

Projection: outputs only specified properties

Select: Output only rows that match the criteria

Natural joins: All rows of the same name with the same value on the property

Cartesian product:

(A+B) (c+d) =AC+AD+BC+BD

And:

Rdb object:

Library table indexed view user stored procedure Store function trigger Event Scheduler

Constraints:

Domain constraints: Data type constraints

FOREIGN KEY constraints: referential integrity constraints

PRIMARY KEY constraint: A field can uniquely represent the entity to which this field belongs, and is not allowed to be empty

A table can have only one primary key

Unique key constraint: A field in each row is not allowed to have the same value, can be empty

A table can have more than one unique key

Check constraint: Age:int

Constraint

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MySQL series one relational database theory