MySQL Basic notes (i)

Relational database concepts:

1. What is a relational database?

　　Relationship Type database: A database built on a relational model (mathematical model)

Relational model: A model that is so-called based on relationships.

The relational model consists of three aspects:

1, data structure: The problem of storage, two-dimensional table (there are rows and columns).

2. Operation instruction set: all SQL statement.

3, integrity constraints: in-Table data constraints (fields and fields), table and table constraints (foreign keys).

2, the design of relational database?

　　Relational database: Analyze from the data needs that need to be stored, if it is a class of data (entities) should be designed as a two-bit table

The table is composed of the header (field name: The name used to specify the data) and the data score (the actual stored data unit)

Relational database: Maintains the relationship between entities and entities within the entity.

One of the characteristics of a relational database: if the corresponding field in the table has no value (data), the system still allocates space.

3. Key words

　　Databases: Database.

Database system: DBS: is a virtual system, speaking a variety of content associated with the name, dbs= dbms+db

Dbms:datebase Management System, database management systems, dedicated management database

Dba:database Administrator, database administrator

Row/record: Row/record, which refers to a row in a table (a record).

column/field: Column/field,

　

sql:structured query Language, structured querying language

　　SQL is divided into three parts:

Ddl:data definition Language, data definition meta, the organization used to maintain stored data (database, table)

Representative instructions such as: Creat,drop,alter, etc.

Dml:data manipulation Language, data manipulation language, used to manipulate data (contents in datasheet)

Representative instructions such as: Insert,delete,update.

Within DML, there is a separate classification dql (data query Language: The language for querying, such as Select).

Dcl:date control Language, data controls language, primarily responsible for Rights management (user)

Representative directive: Grant,revole, etc.

　　　　

MySQL Basic notes (i)