Knowledge of MySQL Learning database

--Database

A database is a warehouse where data is stored.

Databases: Database

Database system DBS: A virtual system that associates a variety of content

DBMS (Database Management System): Specialized database management

Dba:database Administrator: Database administrator

DBS = DBMS + DB

--Classification of databases

Categorized by database based on storage media differences

relational database sql: stored on the hard disk

such as: Oracle, DB2, Sql-server, Mysql, Access .....

Non-relational database nosql: stored in memory

such as: memcached, MongoDB, Redis

--Features of two types of databases:

Relational database:

Secure (stored on disk), easy to understand (built on relational models), no space saving (some word in the data blank still allocates space)

Non-relational database: High efficiency (stored in memory), insecure (loss of data with power outages, but where redis can synchronize data to disk)

--Relational database

Relational databases are built on relational models (mathematical relationships)

Relational model is a model based on relationships (a pair of one or one-to-many, many-to-many)

The relational model includes the data structure (problem of datastore, two-dimensional table),

Operation instruction Collection (SQL statement),

Integrity constraints (data constraints in the table, constraints between tables and tables).

The number field in the table above indicates that this column is the school number (internal constraint); If there is a class in the table, then there is a class table, which is the constraint between the table and the table (through the foreign key).

Knowledge of MySQL Learning database