MySQL database basic command operation
MySQL database basic command operations (add, delete, modify, check)
Basic overview
- Commonly used data types
| int | Integer |
|---|---|
| float | Single precision floating point 4 bytes 32 bits |
| double | Double precision floating point 8 bytes 64 bits |
| char | Fixed-length character type |
| varchar | Variable length character type |
| text | text |
| image | image |
| decimal (5,2) | 5 effective length numbers with 2 digits after the decimal point |
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SQL statement
SQL statement is used to maintain and manage the database, including data query, data update, access control, object management and other functions. -
SQL statement classification
| DDL | Data definition language, used to create database objects, such as libraries, tables, indexes, etc. |
|---|---|
| DML | Data manipulation language, used to manage the data in the table |
| DQL | Data query language, used to find data records that meet the conditions from the data table |
| DCL | Data control language, used to set or change database user or role permissions |
View the database in the current server
SHOW DATABASES; #大小写不区分，分号“;”表示结束
View the tables contained in the database
USE 数据库名;
SHOW TABLES;
View the structure of the table (fields)
USE 数据库名;
DESCRIBE [数据库名.]表名;
可缩写成：DESC 表名;
1 increase
1.1 Create a new database
CREATE DATABASE 数据库名;
1.2 Create a new table
CREATE TABLE 表名 (字段1 数据类型,字段2 数据类型[,...][,PRIMARY KEY (主键名)]);
1.3 Insert a new data record into the data table
INSERT INTO 表名(字段1,字段2[,...]) VALUES(字段1的值,字段2的值,...);
2 Delete
2.1 Delete the specified data table
DROP TABLE [数据库名.]表名; #如不用USE进入库中，则需加上数据库名
2.2 Delete the specified database
DROP DATABASE 数据库名;
2.3 Delete the specified data record in the data table
DELETE FROM 表名 [WHERE 条件表达式];
2.4 delete fields
ALTER TABLE 表名 DROP 字段名;
3 change
3.1 Modify and update data records in the data table
UPDATE 表名 SET 字段名1=字段值1[,字段名2=字段值2] [WHERE 条件表达式];
3.2 Modify the table name
ALTER TABLE 旧表名 RENAME 新表名;
3.3 Expand the table structure (add fields)
ALTER TABLE 表名 ADD address varchar(50) default '地址不详';
3.4 Modify the field (column) name, add a unique key
ALTER TABLE 表名 CHANGE 旧列名 新列名 数据类型 [unique key];
4 check
4.1 View basic information in the table
SELECT 字段名1,字段名2[,...] FROM 表名 [WHERE 条件表达式];
