出1. Login and exit 登 1) Login
Under the DOS command window under the DOS command window under the DOS command window to enter mysql Enter;
Linux Enter the server using Putty to connect to mysql, and then enter: mysql -u username -P password is that it is You can enter the mysql> interface.
2) Exit
Execute exit and press Enter.
3) Change password
mysql -u username-p password password new password
2. Basic database operations
mysql>show databases;
2) Create database
mysql>create database name; //here The name refers to the name of the database that needs to be created.
3) Delete database
Mysql>drop database name; //The name here refers to the name of the database that needs to be deleted.
4) Select the database
Mysql>use databasename; //The databasename here refers to the name of the selected database.
5) Check the currently used database
mysql>select database();
3. Basic operations of the table
1) Display tables s mysql & gt; show tables;
2) Show specific table structure
mysql & gt; description to tableename;
3) Create tables
mysql & gt; create table table (Col1 Type, Col2 Ty per ....); // The tablename here refers to the name of the table to be created.
4) Delete the table
Mysql>drop table tablename; //The tablename here refers to the name of the table to be created.
5) Insert data
into tablename values(col1 value,col2 value....);
6) Query data
select * from tablename where.....;
7) Update data
update tablename set col1 = newvalue where .....;
8) Delete data
delete from tablename where ......;
4. File import
1) Import .sql file command (for example, D:/mysql.sql)
mysql>source d:/mysql.sql;
2) Use text mode to import data into the database table
mysql>load data local infile "filename" into table tablename;
5. User permission operations
1) Add new users
grant all privileges on *.* to username@localhost identified by "password";
3) Add specific operations of the database to the user
Grant select, insert, update on databasename.* to username@localhost identified by "password"
4) Add operation permissions to a certain table in the database to the user
Grant update, delete on databasename.tablename to username@localhost identified by "password"
5) Delete permissions
revoke all privileges on *.* from username@localhost
6) flush privileges;
6. MySQL database backup and migration
1) Remote database backup
mysqldump -h 10.201.10.243 -udiscuz -p discuz >discuz_69.sql
2) Import the backed up database
=> mysql -ushenweiyan -p //Log in to MySQL
use using newucdb;

MySQLstringtypesimpactstorageandperformanceasfollows:1)CHARisfixed-length,alwaysusingthesamestoragespace,whichcanbefasterbutlessspace-efficient.2)VARCHARisvariable-length,morespace-efficientbutpotentiallyslower.3)TEXTisforlargetext,storedoutsiderows,

MySQLstringtypesincludeVARCHAR,TEXT,CHAR,ENUM,andSET.1)VARCHARisversatileforvariable-lengthstringsuptoaspecifiedlimit.2)TEXTisidealforlargetextstoragewithoutadefinedlength.3)CHARisfixed-length,suitableforconsistentdatalikecodes.4)ENUMenforcesdatainte

MySQLoffersvariousstringdatatypes:1)CHARforfixed-lengthstrings,2)VARCHARforvariable-lengthtext,3)BINARYandVARBINARYforbinarydata,4)BLOBandTEXTforlargedata,and5)ENUMandSETforcontrolledinput.Eachtypehasspecificusesandperformancecharacteristics,sochoose

TograntpermissionstonewMySQLusers,followthesesteps:1)AccessMySQLasauserwithsufficientprivileges,2)CreateanewuserwiththeCREATEUSERcommand,3)UsetheGRANTcommandtospecifypermissionslikeSELECT,INSERT,UPDATE,orALLPRIVILEGESonspecificdatabasesortables,and4)

ToaddusersinMySQLeffectivelyandsecurely,followthesesteps:1)UsetheCREATEUSERstatementtoaddanewuser,specifyingthehostandastrongpassword.2)GrantnecessaryprivilegesusingtheGRANTstatement,adheringtotheprincipleofleastprivilege.3)Implementsecuritymeasuresl

ToaddanewuserwithcomplexpermissionsinMySQL,followthesesteps:1)CreatetheuserwithCREATEUSER'newuser'@'localhost'IDENTIFIEDBY'password';.2)Grantreadaccesstoalltablesin'mydatabase'withGRANTSELECTONmydatabase.TO'newuser'@'localhost';.3)Grantwriteaccessto'

The string data types in MySQL include CHAR, VARCHAR, BINARY, VARBINARY, BLOB, and TEXT. The collations determine the comparison and sorting of strings. 1.CHAR is suitable for fixed-length strings, VARCHAR is suitable for variable-length strings. 2.BINARY and VARBINARY are used for binary data, and BLOB and TEXT are used for large object data. 3. Sorting rules such as utf8mb4_unicode_ci ignores upper and lower case and is suitable for user names; utf8mb4_bin is case sensitive and is suitable for fields that require precise comparison.

The best MySQLVARCHAR column length selection should be based on data analysis, consider future growth, evaluate performance impacts, and character set requirements. 1) Analyze the data to determine typical lengths; 2) Reserve future expansion space; 3) Pay attention to the impact of large lengths on performance; 4) Consider the impact of character sets on storage. Through these steps, the efficiency and scalability of the database can be optimized.


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