Database Review Summary (1)-Introduction to the database

I. What is a database

Database: Warehouse db where data is stored

With the development of e-commerce, warehouses are more and more known to everyone, about the warehouse manager's work we also have some understanding

Since ancient times, there are many kinds of warehouses: silos, ammunition depots and other warehouses will also have the warehouse manager (DBA) to manage the goods

The person (programmer) who takes the goods from the warehouse and needs the voucher, the pickup and the stock

Ii. how we store data

History: Ropes Chronicle-"File Storage-" computer

For data not only need storage, more important is to store the data after how to quickly and easily query, modify

Database features: Mass storage, fast lookup, concurrency problem control, security, data integrity (data stored in the database is correct, real)

Advanced applications: BI, expert system, artificial intelligence

III. Overview of the database

DBMS (Database Management system) and database. In peacetime, there may be two meanings of "database": MSSQLServer, Oracle, and other DBMS; a taxonomy of a bunch of data tables (Catalog)

Different brands of DBMS have their own different features: MYSQL (fast, suitable for the data requirements are not very rigorous place, removed many small and medium-sized enterprises infrequently used features), MSSQLServer (and. NET is very good, can only run under the Windows platform, big Data volume, Large volumes do not perform very well), DB2 (Large), Oracle (Large), Access (file), SQLite (extremely lightweight database), Sybase, and so on. For developers, it's very similar.

SQL (language) <>sqlserver<>mssqlserver. The most common error.

In addition to file-based databases such as Access, SqlServerCe, SQLite, most databases require a database server to run. Learning, development is connected to the local database, on-line runtime is the database running on a separate server

Iv. relational database E-r (Entity-Contact Map (entities relationship Diagram))

The current mainstream database, are based on the E-R model of the database

E-r model refers to entity-relation model

The typical feature is that an entity can contain multiple columns, one row to form an entity, and a number of correspondence between entities and entities

The example here is similar to a class in object-oriented, except that it focuses only on the data (fields) that describe the object, not on the object's behavior (function)

V. Concepts in the Database

Database, non-homogeneous data should be placed in a different database

(1) Facilitate personalized management of individual data categories

(2) Avoid naming conflicts

(3) Higher security

Table: [Relationships] in a relational database are tables. different goods have to be placed in their respective cargo racks, which are called "Tables" (table). Different tables are optimized for space based on the data they are placed in, and it is convenient to find them.

Columns, fields (field), row tuples

Format data in tables: Even the introduction of automatic recognition devices is easy to identify.

Vi. Database design: Paradigm (three paradigms)

At this stage, you must comply with 3NF

1 Normal form: (column cannot be divided)

The atomicity of the column, that is, the column is no longer split

2 Paradigm: (Unique identification)

The table cannot describe multiple information and cannot have data redundancy

3 Paradigm: (Reference primary key)

Referencing primary key information for other tables

Database Review Summary (1)-Introduction to the database