⭐️Introduction⭐️
Hello everyone, I am Blue and White Porcelain. Today, I will share with you the basic operation of MySQL. The blogger Xiaobai, if there is any place where the summary is not in place, please point out!
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⭐️ What is a database
The database is a software (a type of software) , and the function of this type of software is "管理数据"to implement the internal database software and widely use various data structures.
The database is the management data, in general, it is saved on the hard disk~
("持久化存储"的方式)
⭐️ Database Classification
Databases can be roughly divided into relational databases and non- relational databases
关系型数据库（RDBMS）: Refers to a database that uses a relational model to organize data. Simply put, a relational model refers to a two-dimensional table model, and a relational database is a data organization composed of two-dimensional tables and the connections between them.
1. Oracle: Oracle product, suitable for large-scale projects, suitable for Complex business logic, such as ERP, OA, etc., charges and prosthetics are expensive 2.
MySQL: belongs to Oracle, not suitable for complex business, open source free
Large projects, fee
非关系型数据库:
SQL-based implementation is not specified. Now it refers more to NoSQL database
1. Based on key-value pair (Key-Value)
2. Based on document type: such as mongodb
Generally, we use MySQL in the process of learning:
MySQL database is a '客户端-服务器'structural program
The party that initiates the request actively is called the party that
客户端
passively receives the request, it is called服务器
the data sent by the client to the server, it is called"请求"
the data returned by the server to the client, it is called"响应"
MySQL we use about four cases~
⭐️ Operation of the database
⭐️ Show current database
Grammar: show databases;
Note: There is a space between show and databases, which can be one or more, but not without!
⭐️Create database
Grammar : create database 数据库名字;
Note : When some students are just learning MySQL, one of the most likely mistakes is 单词的拼写, so we must pay attention when using MySQL! The meaning of the horizontal line here means that操作成功了!花的时间为0.00 秒~
Here's an addition, if we enter the sql statement and encounter execution failure, there will be an error message. At this time, don't panic. In fact, the error message is the simplest and most basic English, and you only need to be patient to understand it. It's just that some students get scared when they see English~
⭐️ Use database
grammar: use 数据库名;
⭐️ delete database
Grammar: drop database; 数据库名;
Note: This operation is very dangerous!! Once executed successfully! At this time, the data will not be returned with a high probability, (cool, bbq!)
⭐️ Common data types
It mainly includes the following five categories:
Integer types: BIT, BOOL, TINY INT, SMALL INT, MEDIUM INT, INT, BIG INT
Floating point type: FLOAT, DOUBLE, DECIMAL
String types: CHAR, VARCHAR, TINY TEXT, TEXT, MEDIUM TEXT, LONGTEXT, TINY BLOB, BLOB, MEDIUM BLOB, LONG BLOB
Date Type: Date, DateTime, TimeStamp, Time, Year
Other data types: BINARY, VARBINARY, ENUM, SET, Geometry, Point, MultiPoint, LineString, MultiLineString, Polygon, GeometryCollection, etc.
⭐️ Numeric Type
⭐️ String type
⭐️ Date Type
⭐️ Table operations
⭐️ View table
Grammar: show tables;
The premise of this operation must also be先选中数据库~
⭐️ View table structure
grammar: desc 表名;
Notice:
⭐️Create table
Syntax: create table 表名;
Note: Before the operation of creating a table,要先选中数据库(use 数据库名;)
If you create a table directly, it cannot be created
. The correct way is to select the database first and then create the table.
⭐️ delete table
grammar: drop table 表名;
After deleting, looking at our table again, we will see that it is gone.
Note:
Deleting a table is also a very dangerous operation! Everyone must be careful, once it is deleted, it may not be restored!!~