MySQL operates the database through the CMD command line, and the image cannot be found during the real machine debugging of fluent

Run as administrator cmd Command line   →  Input net start mysql  → enter

Stop the service and use the command ：net stop mysql

3、 ... and 、 Connect MYSQL

=========

Format ：

mysql -h The host address -u user name -p User password

-h The host address can be omitted

Example ：

Suppose the user name is root The password for 123456

mysql -hlocalhost -uroot -p123456

mysql -uroot -p123456

sign out MYSQL command ： exit ( enter )

Four 、 Change user name and password

=========

Format ：

mysqladmin -u user name -p Old password password New password

Example ：

to root The user sets the password as 123456

mysqladmin -u root -password 123456

then root The user password is changed to 123123

mysqladmin -u root -p 123456 password 123123

Command line modification root password ：

mysql> UPDATE mysql.user SET password=PASSWORD(‘ New password ’) WHERE  User=‘root’;

mysql> FLUSH PRIVILEGES;

5、 ... and 、 Common operation commands of database

===========

1、 Show database list ：

mysql> SHOW DATABASES;

2、 Building a database ：

mysql> CREATE DATABASE Library name ;

3、 Delete database ：

mysql> DROP DATABASE Library name ;

4、 Create data tables ：

mysql> CREATE TABLE Table name ( Field name VARCHAR(20), Field name CHAR(1));

5、 Modify the field name and properties

mysql> alter table Table name change Field name   new field name varchar(50);

6、 Fields inserted into the table

mysql> alter table Table name add newColumn varchar(8) NOT NULL COMMENT ‘ Newly added fields ’;

7、 Delete data table ：

mysql> DROP TABLE Table name ;

8、 Empty the records in the table ：

mysql> DELETE FROM Table name ;

9、 Modify the name of the table ：

mysql> alter table t1 rename t2

10、 Query table data ：

mysql> select * from Table name ;

11、 Insert a record into a table ：

mysql> INSERT INTO Table name VALUES (“ Zhang San ”,“20”);

10、 Update the data in the table ：

mysql> UPDATE Table name SET Field name 1=‘a’, Field name 2=‘b’ WHERE Field name 3=‘c’;

11、 Load data into a data table in text form ：

mysql> LOAD DATA LOCAL INFILE “D:/mysql.txt” INTO TABLE Table name ;

12、 Import .sql File command ：

mysql> USE Database name ;

mysql> SOURCE d:/mysql.sql;

6、 ... and 、 Sample code

======

1、 Create database

drop database if exists mydata; // If there is mydata Delete

create database mydata; // Create a mydata The database of

use mydata; // Open database mydata

2、 Create data table

grammar ：

CREATE TABLE table_name(col_name col_type col_attr, col_name col_type col_attr,……)

Parameters ：

A data table , Composed of multiple columns , Multiple column definitions are separated by commas in English .

col_name： Column name .

col_type： The type of the column . Such as ：tinyint、int、bigint、char、varchar、text、date、time etc. .

col_attr： Column properties .

NOT NULL | NULL： Whether the column can be empty .

DEFAULT default_value： Refers to the default value of this column ,default_value The default value can be a string , It can also be integer .

AUTO_INCREMENT： This column is auto growth , Or automatic numbering . The column must be integer . A table can only have one auto_increment attribute .

PRIMARY KEY： Primary key , Specifies that the value of this column is unique , The column where the primary key is located cannot be empty . The primary key of a table can only have one .

id The properties of the field must have ：NOT NULL AUTO_INCREMENT PRIMARY KEY, In this way, the serial number can increase itself .

Example ：

create table user

(

id int(11) auto_increment not null primary key,

name varchar(20) not null COMMENT ‘ name ’,

age int(3) not null default 0 COMMENT ‘ Age ’,

address varchar(50) default ‘ Shenzhen ’ COMMENT ‘ Address ’,

year date

);

3、 Insert data into table

insert into user values(‘ Zhang San ’,18,‘ Shenzhen ’,‘2021-10-10’);

insert into user values(‘ Li Si ’,20,‘ Guangzhou ’,‘2021-10-15’);

7、 ... and 、 Backup database

=======

1、 Export the entire database （ The export file exists by default mysql\bin Under the table of contents ）

Last

Actually Android There are so many knowledge points in development , There are still so many things to ask about in the interview . So there's no other trick to an interview , It depends on how well you are prepared for these knowledge points .so, When you go out for an interview, you should first see which stage you have reviewed .

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Due to limited space , Here's a small part of it in the form of pictures .

Detailed arrangement in GitHub You can see ;

Android Architecture video +BAT Interview topics PDF+ Learning notes ​

Online learning Android A lot of information , But if the knowledge learned is not systematic , When you encounter a problem, you just have a taste of it , No further study , So it's hard to really improve the technology . I hope this systematic technical system has a direction reference for you .

Detailed arrangement in GitHub You can see ;

Android Architecture video +BAT Interview topics PDF+ Learning notes ​

Online learning Android A lot of information , But if the knowledge learned is not systematic , When you encounter a problem, you just have a taste of it , No further study , So it's hard to really improve the technology . I hope this systematic technical system has a direction reference for you .