MYSQL Chapter 1 Introduction to Databases

Chapter 1 Introduction to Databases

1-1 MySQL Database Course Outline

Introduction to MySQL Database

Databases can be stored in memory, text, databases

Common databases and applicable scenarios

The most commonly used are: Oracle, MySQL
University generally learn: SQLServer

MySQL database installation and use

Introduction to SQL Statements

After the database is installed successfully, you can operate it through SQL statements

Classification of SQL Statements, DDL, DML, DQL, DCL

DDL statements operate the database and
DML statements such as create, drop, and alter of the table to insert, delete, and update
the table data. DQL statements perform various dimension select queries on the table data

• Simple query
• Conditional query
• fuzzy query
• Group query

MySQL database constraints

Guarantee the correctness, validity and integrity of the data

• primary key constraint
• unique constraint
• Not Null Constraint

1-2 Overview and advantages and disadvantages of the database

What is a database
A warehouse that stores data is essentially a file system.

How the data is stored

1. data is kept in memory

• Pros: fast memory
• Disadvantages: power failure/program exit, data is cleared, memory is expensive

2. Data is saved in ordinary files

• Advantages: permanent storage
• Disadvantages: finding, adding, modifying, and deleting data is troublesome and inefficient

3. data is stored in the database

• Advantages: permanent storage, convenient operation of the database through SQL statements

1-3 Characteristics of common databases and their application scenarios

• MySQL open source free database, small database, has been acquired by oracle
• Large-scale databases charged by Oracle, Oracle's products, database list No. 1
• DB2 IBM database product, chargeable, often used in banking systems , the software and hardware are produced by the same company, the database has high compatibility and stability
• SQLserver is a medium-sized database charged by Microsoft, commonly used in C#, .net and other languages
• SyBase has faded out of the historical stage, providing a very professional database modeling tool PowerDesigner (database modeling tool)
• SQLite embedded small database, applied on mobile phone

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Commonly used databases: MYSQL, Oracle

In web applications, the most used MySQL database is:

• Open source (optimized and perfect), free
• The function is powerful enough to cope with web application development, and supports up to tens of millions of concurrent accesses