1、像网页上的账户、图片、文章都是存在数据库里面
2、Oracle 、DB2 、SQL server等等多钟数据库
PHP中选择使用mysql PHP+mysql黄金搭档
PHP和mysql都是开源的,免费实用,配置性好。
mysql中小型适合,但没有Oracle强大。
3、mysql的架构:C/S client/server
在server端开启,client端操作
mysql DBMS(DB代表数据库 M代表管理 S代表系统)
客户端操作 服务器端---数据库--数据表--(行(记录),行(字段))
4、程序员要学的mysql
1、为你的项目设计表
2、使用sql语句(sql编程--连接,数据增删改查)
可以使用工具完成。
5、mysql安装,和php整合
目录结构:my.ini配置文件 :自己修改端口、字符集等等
启动服务器:(1)自带启动入口(2)计算机管理/服务/找到mysql服务一项可以启动
(3)用cmd命令启动:net strat/stop/restrat mysql 启动服务
linux环境下 是service mysqld strat
配置环境变量:计算机属性搭配环境变量path。吧对应的目录放在path的变量值里面
路径之间用分号隔开。在cmd命令行下先在里面的路径查找该命令
6、数据库sql的语句操作
SQL (structured Query language)
DDL创建表
DML数据操作 增删改查
DQL数据查询
DCL数据控制语句(管理权限,数据更改)
1、执行sql语句,链接到数据库服务器
cmd命令:mysql -h(地址)IP地址/本机:localhost -u(指定用户) root -p123456(密码)
提示mysql>进入 exit退出
要留一个管理员用户
DDL:
create database liangcha(库名称)
drop database liangcha (删除库)(相当于新建删除文件夹)
create database if not exists liangcha
create table liangcha user(id int,name char);
选择一个库作为默认数据库,方便操作
use liangcha;
show database/table;(查看)
DML:
insert into user(id,name) values
updata user set name='lili' where id='1' (修改把id为1的那个名字修改为lili)
delete from user where id=‘1’ (删除) where=操作的条件
DQL:
select * from user(查询表)
DCL:
/s看状态
show databases 看所有库
show tables 看所有表
desc 看表结构
show varlable 配置文件中的变量

MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

MySQL is an open source relational database management system suitable for data storage, management, query and security. 1. It supports a variety of operating systems and is widely used in Web applications and other fields. 2. Through the client-server architecture and different storage engines, MySQL processes data efficiently. 3. Basic usage includes creating databases and tables, inserting, querying and updating data. 4. Advanced usage involves complex queries and stored procedures. 5. Common errors can be debugged through the EXPLAIN statement. 6. Performance optimization includes the rational use of indexes and optimized query statements.

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.

InnoDB's lock mechanisms include shared locks, exclusive locks, intention locks, record locks, gap locks and next key locks. 1. Shared lock allows transactions to read data without preventing other transactions from reading. 2. Exclusive lock prevents other transactions from reading and modifying data. 3. Intention lock optimizes lock efficiency. 4. Record lock lock index record. 5. Gap lock locks index recording gap. 6. The next key lock is a combination of record lock and gap lock to ensure data consistency.

The main reasons for poor MySQL query performance include not using indexes, wrong execution plan selection by the query optimizer, unreasonable table design, excessive data volume and lock competition. 1. No index causes slow querying, and adding indexes can significantly improve performance. 2. Use the EXPLAIN command to analyze the query plan and find out the optimizer error. 3. Reconstructing the table structure and optimizing JOIN conditions can improve table design problems. 4. When the data volume is large, partitioning and table division strategies are adopted. 5. In a high concurrency environment, optimizing transactions and locking strategies can reduce lock competition.

In database optimization, indexing strategies should be selected according to query requirements: 1. When the query involves multiple columns and the order of conditions is fixed, use composite indexes; 2. When the query involves multiple columns but the order of conditions is not fixed, use multiple single-column indexes. Composite indexes are suitable for optimizing multi-column queries, while single-column indexes are suitable for single-column queries.

To optimize MySQL slow query, slowquerylog and performance_schema need to be used: 1. Enable slowquerylog and set thresholds to record slow query; 2. Use performance_schema to analyze query execution details, find out performance bottlenecks and optimize.

MySQL and SQL are essential skills for developers. 1.MySQL is an open source relational database management system, and SQL is the standard language used to manage and operate databases. 2.MySQL supports multiple storage engines through efficient data storage and retrieval functions, and SQL completes complex data operations through simple statements. 3. Examples of usage include basic queries and advanced queries, such as filtering and sorting by condition. 4. Common errors include syntax errors and performance issues, which can be optimized by checking SQL statements and using EXPLAIN commands. 5. Performance optimization techniques include using indexes, avoiding full table scanning, optimizing JOIN operations and improving code readability.


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