Mysql database basic operation -ddl | dark horse programmer

MySQL Strong performance , It is one of the most widely used databases at present , With  MySQL For learning the prototype, it is also convenient to master other databases later , Now let's give you Give a comprehensive explanation MySQL8.0 New features , From zero foundation to high-level one-stop learning , Combined with actual cases, we can gain something ！

▼ MySQL8.0 introduction - Advanced learning notes ：（ Summary ）

•   The first 1 speak ：SQL Overview and database system introduction | Black horse programmer
•   The first 2 speak ：MySQL brief introduction 、 Detailed installation steps and use | Black horse programmer
• The first 3 speak ：MySQL Common graphics management tools | Black horse programmer

---

1、DDL explain

DDL(Data Definition Language), Data definition language , The language section includes the following ：

• Common operations on Database
• Common operations on table structure
• Modify table structure

​

2、 Common operations on Database

​

Common operations on table structure - Create table

• Create a table format

​

Creating a table is to build an empty table , Specify the name of this table , This table has several columns , What is the name of each column , And the type of data stored in each column .

​

• data type

Data type refers to specifying the data type for the fields in the table when creating the table , Only if the data meets the type requirements can it be stored , The principle of using data types is : Enough is enough. , Try to use a small range of , Not the big one , This can save more storage space .

• value type

​

• Date and time type

​

• String type

​

3、 Common operations on table structure — Other operating

​

• Modify the table to add columns

Grammar format

alter table  Table name  add  Name   type ( length ) [ constraint ];

Example ：

# by student Add a new field to the table as ： Is don't  dept  The type is  varchar(20)
ALTER TABLE student ADD `dept` VARCHAR(20); 

• Change column name and type

Grammar format

alter table  Table name  change  Old column names   New column names   type ( length )  constraint ; 

Example

# by student Tabular dept Replace field with department varchar(30)
ALTER TABLE student change `dept` department VARCHAR(30);

• Modify table delete column

Grammar format

alter table  Table name  drop  Name ;

Example

# Delete student In the table department This column 
ALTER TABLE student DROP department;

• Modify the name of the table

Grammar format

rename table  Table name  to  The new name of the table ;

Example

# Will table student Change its name to  stu
rename table `student`  to stu;