Get to know MySQL for the first time

1.MySQL History and characteristics of

history ： From Sweden MySQL AB Establishment of the company ,1995 Developed MySQL 2008 year ,MySQL By SUN Company purchase 2009 year ,Oracle Acquisition SUN company , , in turn, Oracle You get MySQL 2016 year ,MySQL8.0.0 Version launch

characteristic ： Open source 、 Relational databases Support the storage of tens of millions of data , Large databases

1. Persistence ： Save data to a power down storage device for later use .

Data persistence means saving the data in memory to the hard disk “ curing ”.

The main function of persistence is to store the data in memory in the relational database .

2. understand MySQL

DB：database, A database is a file . （ Be similar to ：.doc、.txt、.mp3、.avi、...）

DBMS： Database management system .（ Be similar to word Tools 、wps Tools 、 Notepad tools 、qq Video player, etc ） MySQL The database server is installed with MySQL DBMS, Use MySQL DBMS To manage and operate DB, It uses SQL Language .

SQL: Structured query language

A language designed to communicate with a database

RDBMS: Relational database

Relational database to line （row） And column （column） In the form of data storage

ORM thought

A table in the database <-->Java A class in

A piece of data in the table <--> An object in a class （ Or entity ）

A column in the table <--> A field in a class , attribute （field）

The relationship between tables

One to one connection , One to many connection , Many to many connection , Self quoting

3.SQL The classification of

DDL: Data definition language

DML： Data operation language （ Include SELECT Query statement , a key ）

DCL： Data control language