search
HomeDatabaseMysql TutorialA large collection of MySQL sql basic statements

I am accustomed to using SQL Sever to directly design the database every time, but do not pay enough attention to SQL statements. I took the opportunity of this reconstruction of the computer room cooperation version to use SQL statements to design the database and at the same time Let’s sort out the basic usage of SQL statements.

【Classification】

There are 9 types of SQL statements, which can be roughly divided into 4 types according to their functions:

1. Query statement: select ----The most commonly used statement in the database

2. Data definition: create, drop, alter----for Operations on databases, data tables, and fields in tables

3. Data manipulation: insert, update, delete----the legendary "add, delete, modify, query", for specific Data operations

4. Data control: grant, revoke----definition and deletion of permissions

[Statement summary]

1. Create a database

##

create database RechargeSystem
on primary    --主文件组
(
	/*数据文件的具体描述*/
	name='RechargeSystem_data',  --主数据文件的逻辑名称
	filename='G:\RechargeSystem\RechargeSystem_data.mdf',  --主数据文件的物理名称
	size=5mb,       --初始大小
	maxsize=100mb,  --增长最大值
	filegrowth=15%   --主数据文件增长率
)
log on
(
	/*日志文件的具体描述*/
	name='RechargeSystem_log',
	filename='G:\RechargeSystem\RechargeSystem_log.ldf',
	size=2mb,
	filegrowth=1mb
)

If you have learned the operating system, you will not be very familiar with these definition statements. Strangely enough, a database group file is also a kind of file and needs to have a logical name (i.e. file name), physical name (actual storage address on the disk), file size, etc.; the log file records all logical operations in the database, with details such as advantages and disadvantages. For the content, see Baidu Encyclopedia: Log file


2. Basic table operations

--------------------------------------------------------------------------------------------------------------------------------------------
       create table <基本表名>   ---建立表格
               (<列名 类型 not null>,
                 primary key(列名,列名),--主键约束
                 foreign key (<列名>) references tableName(<列名>),--外键约束);
--------------------------------------------------------------------------------------------------------------------------------------------
      alter table <表名> add <列名><数据类型>  --添加列

You can set the primary and foreign keys of the established table:
##

  alter table <表名> add primary key(<列名>,<列名>)
      alter table<表名> add foreign key(<列名>) references tableName(<列名>)

Delete a column: alter table drop [cascade|restrict] --restrict will Views and constraints are also sectored


---------------------- -------------------------------------------------- -------------------------------------------------- ------------------

## drop table

[cascade|restrict] --Delete table, with constraints Restrict

must be added to the condition

3. Query statement:

Regular The query statement is: select * from datatable


It should be noted that nested and connected queries are queried from multiple tables. This combination relationship is commonly used in M:N relationships. Find the corresponding relationship.

 select TB1.column1,TB1.column2
                from TB1
                where TB1.column1 in(select column1
                                                         from TB2
                                                        where TB2.column2="特定值");


This relationship is not recommended for users with confusing logic, as it is particularly likely to cause search failure.

---------------------------------------- -------------------------------------------------- -------------------------------------------------- --

In addition, the SQL query statement also provides basic aggregate functions for easy query use:

count(*) --- --------------------Calculate the number of tuples, that is, how many columns there are in total

count()----------------Calculation of the number of values ​​in a column

sum()-- ------------------The sum of a column of values ​​(numeric type)

avg ()-- -------------Average (must be numeric type)

max()-------- ---------Maximum value

## min()------------------ ----Minimum value

#--------------------------------------------- -------------------------------------------------- --------------------------------------------------

Complete semantic structure:

                                                                                                                                                                 ’’’''‐‐' '' #''''''''‐'‐'‐'‐‐‐‐---- where

## group by ----------------------- ---------Grouping based on a certain field

## Having -------------- ------Information that does not meet the group conditions is filtered out

## Order by ---------- --------Asc ascending order, desc descending order

----------------------- -------------------------------------------------- -------------------------------------------------- -------------------

## Special query requirements:

1. Comparison Operations: ,>=,!=

## 2. Matching operation: %---matches characters consisting of zero or more characters , "_" single character matches

3. Null value is Null

4. Aggregated resource comparison: in, some, any, all

5. Whether the set is non-empty: exits --- If it is not empty, it is true, otherwise it is false

6. Whether there are duplicates in the set Tuple: unique--------repeat to true, otherwise false

-------------------------- -------------------------------------------------- -------------------------------------------------- -----------------------

4. Data operation statements

Insert: insert into

(, ...) values('value', 'value')

Delete: delete from

where condition

Modify: update

set ##5. Embedded SQL usage technology, commonly used execution views, stored procedures, etc., add exec to execute

[Summary]

Knowledge is always like this , you will gain different results every time you study, especially after using it, you will try to compare the differences between different methods. I look forward to the next comparative study of database views, stored procedures and security settings.

The above is the content of a large collection of MySQL sql basic statements. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!

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
MySQL: Essential Skills for Beginners to MasterMySQL: 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 DatabasesMySQL: 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 ExplainedMySQL: 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 DatabasesThe 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 ManagementMySQL 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

MySQL's Role: Databases in Web ApplicationsMySQL's Role: Databases in Web ApplicationsApr 17, 2025 am 12:23 AM

The main role of MySQL in web applications is to store and manage data. 1.MySQL efficiently processes user information, product catalogs, transaction records and other data. 2. Through SQL query, developers can extract information from the database to generate dynamic content. 3.MySQL works based on the client-server model to ensure acceptable query speed.

MySQL: Building Your First DatabaseMySQL: Building Your First DatabaseApr 17, 2025 am 12:22 AM

The steps to build a MySQL database include: 1. Create a database and table, 2. Insert data, and 3. Conduct queries. First, use the CREATEDATABASE and CREATETABLE statements to create the database and table, then use the INSERTINTO statement to insert the data, and finally use the SELECT statement to query the data.

MySQL: A Beginner-Friendly Approach to Data StorageMySQL: A Beginner-Friendly Approach to Data StorageApr 17, 2025 am 12:21 AM

MySQL is suitable for beginners because it is easy to use and powerful. 1.MySQL is a relational database, and uses SQL for CRUD operations. 2. It is simple to install and requires the root user password to be configured. 3. Use INSERT, UPDATE, DELETE, and SELECT to perform data operations. 4. ORDERBY, WHERE and JOIN can be used for complex queries. 5. Debugging requires checking the syntax and use EXPLAIN to analyze the query. 6. Optimization suggestions include using indexes, choosing the right data type and good programming habits.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
Will R.E.P.O. Have Crossplay?
1 months agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Safe Exam Browser

Safe Exam Browser

Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

WebStorm Mac version

WebStorm Mac version

Useful JavaScript development tools

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

Atom editor mac version download

Atom editor mac version download

The most popular open source editor