MySQL中的SQL特征[图]_MySQL-Mysql Tutorial-php.cn

Home

Database

Mysql Tutorial

MySQL中的SQL特征[图]_MySQL

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jun 01, 2016 pm 01:56 PM

interfaceserver

为了与MySQL服务器进行通信，必须熟练掌握SQL。例如，在使用诸如mysql客户机这样的程序时，其功能首先是作为一种发送SQL 语句给服务器执行的工具。而且，如果编写使用编程语言所提供的MySQL接口的程序时，也必须熟悉SQL 语言，因为需要发送SQL 语句与服务器沟通。

第1章“MySQL与SQL介绍”的教程介绍了许多MySQL功能。本章在该教程的基础上进一步对MySQL的SQL的几个方面进行研究。它讨论了怎样引用数据库的要素，包括命名规则以及区分大小写约束的适用性。它还介绍了许多更为重要的SQL 语句，诸如创建和删除数据库、表和索引的语句；利用连接检索数据的语句；提供关于数据库和表的信息的语句等。这里的介绍还强调了MySQL对标准SQL 进行的某些扩充。

3.1MySQL中的SQL特征

MySQL的SQL 语句可分为几大类，如图3-1所示。我们将在本章中介绍图3 - 1中所示的前四类。MySQL的一些实用工具提供了与某些SQL 语句的基本命令行接口的机制。例如，mysqlshow 就是SHOW COLUMNS 语句的一个接口。本章中适当的地方也对这些等效的东西进行介绍。未在本章介绍的一些语句将在其他章中介绍。例如，用于设置用户权限的GRANT和REVOKE 语句在第11章“常规的MySQL管理”中介绍。所有语句的引用语法在附录D“SQL 语法参考”中列出。此外，还可以参看MySQL参考指南（ MySQLReference Manual）以获得其他信息，特别是获得MySQL最新版本中所作更改的信息。

MySQL中的SQL特征[图]_MySQL

本章最后一节介绍MySQL缺少的功能，即一些其他数据库中有的而MySQL中无的功能。例如子选择、事务处理、引用完整性、触发器、存储过程以及视图。缺少这些功能是否意味着MySQL不是一个“真正”的数据库系统？有些人是这样认为的，但据笔者的看法，这些功能的缺乏并未阻止大量人员使用它。这大概是因为，对于大多数应用来说，缺这些功能没什么关系。而其他一些需要这些功能的场合，也有相应的解决办法。例如，缺少级联删除表示从表中删除记录时，可能需要发布一条额外的查询。如果发现利用L O C KTABLES 与UNLOCK TABLES 语句，将各语句分为不中断执行组的MySQL功能已经足够，那么缺少事务处理支持对你来说可能不会产生什么影响。（这里真正的问题不是缺少事务处理；而是自动回退以取消失败的语句。如果有一些应用具有复杂的财务事务处理，比如需要完成涉及必须作为一个组执行的几个互锁语句的处理，那么可能会考虑使用具有提交/回退能力的数据库，如使用P o s t g r e s。）某些缺少的功能将在未来实现。如，MySQL不支持子查询，但已计划在版本3 . 2 4中给出，或许您读到本书时它已经实现了

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Explain the InnoDB Buffer Pool and its importance for performance.Apr 19, 2025 am 12:24 AM

InnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.

MySQL vs. Other Programming Languages: A ComparisonApr 19, 2025 am 12:22 AM

Compared with other programming languages, MySQL is mainly used to store and manage data, while other languages such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages have advantages in their respective fields such as data analytics, enterprise applications, and system programming.

Learning MySQL: A Step-by-Step Guide for New UsersApr 19, 2025 am 12:19 AM

MySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.

MySQL: Essential Skills for Beginners to MasterApr 18, 2025 am 12:24 AM

MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL: Structured Data and Relational DatabasesApr 18, 2025 am 12:22 AM

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

MySQL: Key Features and Capabilities ExplainedApr 18, 2025 am 12:17 AM

MySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.

The Purpose of SQL: Interacting with MySQL DatabasesApr 18, 2025 am 12:12 AM

SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

MySQL for Beginners: Getting Started with Database ManagementApr 18, 2025 am 12:10 AM

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA

See all articles