德国老妇激情性xxxx,凹凸在线无码免费视频,国产av麻豆mag剧集

Article Tags

All
web3.0
- All
- NoSQL database
- Memcached
- cloudera
- memcache
Backend Development
- All
- PHP Tutorial
- Python Tutorial
- Golang
- XML/RSS Tutorial
- C#.Net Tutorial
- C++
- NoSQL database
- Memcached
- cloudera
- memcache
Web Front-end
Database
- All
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Operation and Maintenance
- All
- Mac OS
- Linux Operation and Maintenance
- Apache
- Nginx
- CentOS
- Docker
- NoSQL database
- Memcached
- cloudera
- memcache
Development Tools
- All
- VSCode
- sublime
- notepad
- git
- composer
- NoSQL database
- Memcached
- cloudera
- memcache
PHP Framework
- All
- Laravel
- YII
- NoSQL database
- Memcached
- cloudera
- memcache
Common Problem
- All
- NoSQL database
- Memcached
- cloudera
- memcache
Other
- All
- IIS
- SEO
- Premiere
- NoSQL database
- Memcached
- cloudera
- memcache
Tech
- All
- AI
- It Industry
- NoSQL database
- Memcached
- cloudera
- memcache
CMS Tutorial
- All
- WordPress
- NoSQL database
- Memcached
- cloudera
- memcache
Java
- All
- javaTutorial
- NoSQL database
- Memcached
- cloudera
- memcache
System Tutorial
- All
- Windows Series
- LINUX
- MAC
- NoSQL database
- Memcached
- cloudera
- memcache
Computer Tutorials
Hardware Tutorial
Mobile Tutorial
- All
- Mobile News
- iPhone
- Android Phone
- NoSQL database
- Memcached
- cloudera
- memcache
Software Tutorial
Mobile Game Tutorial

Home

Technical Articles

Database

Mysql Tutorial

What is the difference between DELETE, TRUNCATE, and DROP in MySQL?

DELETE is used to delete specific or all rows in a table, supporting WHERE conditions, transaction rollback and triggers, but the speed is slow and the self-increment counter does not reset; TRUNCATE quickly deletes all rows by recreating the table, which is fast and the self-increment counter is reset, but it cannot rollback and does not trigger the trigger; DROP deletes the entire table structure and data, which cannot be rolled back, which is suitable for completely removing tables.

Aug 12, 2025 am 09:26 AM

mysql Data deletion

How to rename a table in MySQL

To rename MySQL table, you should use the RENAMETABLE statement; its basic syntax is RENAMETABLEold_table_nameTOnew_table_name; for example, RENAMETABLEusers_oldTOusers; 1. Single table renaming: one or more tables can be renamed at a time; 2. Atomic operation: During the renaming period, the table is locked and unavailable until it is completed; 3. Permission requirements: ALTER and DROP permissions are required for the original table, and CREATE and INSERT permissions are required for the database; 4. Storage engine compatibility: supports mainstream engines such as InnoDB and MyISAM; multiple tables can be renamed at once using RENAMETABLE.

Aug 12, 2025 am 08:06 AM

How to monitor query cache performance in MySQL

CheckQcachestatusvariablesusingSHOWSTATUSLIKE'Qcache%'tomonitorhits,inserts,prunes,andmemoryusage;2.Calculatehitratewith(Qcache_hits/(Qcache_hits Qcache_inserts))*100,aimingfor70–80%orhigher;3.AssessmemoryefficiencybyanalyzingQcache_free_memoryandfra

Aug 12, 2025 am 05:55 AM

How to list all users in MySQL

TolistallusersinMySQL,executeSELECTUser,HostFROMmysql.user;afterlogginginwithsufficientprivileges.2.Fordetailedinformationsuchasauthenticationpluginandaccountstatus,useSELECTUser,Host,authentication_string,plugin,account_locked,password_expiredFROMmy

Aug 12, 2025 am 05:52 AM

How to find the length of a string in MySQL

TofindthelengthofastringinMySQL,useLENGTH()forbytesorCHAR_LENGTH()forcharacters.1.LENGTH()returnsthenumberofbytes,soSELECTLENGTH('Hello')returns5,butSELECTLENGTH('café')returns5inUTF8mb4because'é'uses2bytes.2.CHAR_LENGTH()returnsthenumberofcharacters

Aug 12, 2025 am 05:01 AM

How to add a primary key to an existing table in MySQL?

To add a primary key to an existing table, use the ALTERTABLE statement with the ADDPRIMARYKEY clause. 1. Ensure that the target column has no NULL value, no duplication and is defined as NOTNULL; 2. The single-column primary key syntax is ALTERTABLE table name ADDPRIMARYKEY (column name); 3. The multi-column combination primary key syntax is ALTERTABLE table name ADDPRIMARYKEY (column 1, column 2); 4. If the column allows NULL, you must first execute MODIFY to set NOTNULL; 5. Each table can only have one primary key, and the old primary key must be deleted before adding; 6. If you need to increase it yourself, you can use MODIFY to set AUTO_INCREMENT. Ensure data before operation

Aug 12, 2025 am 04:11 AM

mysql primary key

How to use the SET data type in MySQL

TheSETdatatypeinMySQLstoreszeroormorevaluesfromapredefinedlist,idealformultiplechoiceslikepreferencesortags.2.DefineaSETcolumnbyspecifyingallowedstringvaluesinparenthesesduringtablecreation,suchasSET('email','sms','push','mail').3.Insertvaluesascomma

Aug 12, 2025 am 04:08 AM

How to use the ALTER TABLE statement in MySQL?

ALTERTABLEinMySQLisusedtomodifyanexistingtable’sstructure,andthemostcommonoperationsinclude:1.AddingacolumnusingADDCOLUMN,optionallyspecifyingpositionwithAFTERorFIRST;2.DroppingacolumnusingDROPCOLUMN,whichpermanentlyremovesthecolumnanditsdata;3.Modif

Aug 12, 2025 am 03:52 AM

mysql

How to use the LIMIT clause in MySQL?

Use LIMIT to limit the number of rows returned by the query, such as SELECTFROMemployeesLIMIT5 returns up to 5 rows; 2. Combining ORDERBY can ensure the order, such as SELECTFROMemployeesORDERBYsalaryDESCLIMIT3 to obtain the highest salary of 3 employees; 3. Use OFFSET to implement paging, such as LIMIT5OFFSET10 means skipping the first 10 rows and returning 5 rows, which is equivalent to LIMIT10,5; 4. It is often used to paging, obtain the first N records or data sampling; 5. Note that the order should always be guaranteed with ORDERBY. LIMIT is MySQL-specific syntax, and high offset may affect performance. It is recommended that

Aug 12, 2025 am 03:32 AM

mysql limit

How to analyze the slow query log in MySQL

First, make sure to enable and correctly configure the slow query log, set slow_query_log=ON, long_query_time=1.0, and log_queries_not_using_indexes=ON, and restart MySQL or dynamic application configuration; 2. Use mysqldumpslow tool to analyze the log, view the most frequent slow query through mysqldumpslow-sc-t10, or filter specific tables with the -g parameter; 3. Use pt-query-digest in PerconaToolkit for in-depth analysis, generate detailed statistics and optimization suggestions, such as identifying that Rows_examined is much larger than Ro

Aug 12, 2025 am 02:13 AM

How to add a column to a table in MySQL

To add columns to an existing MySQL table, you need to use the ALTERTABLE statement to match the ADDCOLUMN clause; the basic syntax is ALTERTABLEtable_nameADDCOLUMNcolumn_namedata_type[constraints], where the COLUMN keyword can be omitted; for example, add VARCHAR column: ALTERTABLEusersADDCOLUMNemailVARCHAR(100); add columns with NOTNULL constraints: ALTERTABLEusersADDCOLUMN created_atDATETIMENOTNULL; add a lever to a VARCHAR column; add a lever to a VARCHAR column: ALTERTABLEusersADDCOLUMN created_atDATETIMENOTNULL; add a lever to a VARCHAR column: ALTERTABLEusersADDCOLUMNcreated_atDATETIMENOTNULL; add a lever to a VARCHAR column: ALTERTABLEusersADDCOLUMNcreated_atDATETIMENOTNULL; add a lever to a VARCHAR column: ALTERTABLEusersADDCOLUMNcreated_atDATETIMENOTNULL; add a lever to a VARCHAR column: ALTERTABLEusersADDCOLUMNcreated_atDATETIMENOTNULL; add a lever to a VARCHAR column: ALTERTABLEusersADDCOLUMNcreated_atDATETIMENOTNULL;

Aug 12, 2025 am 01:56 AM

How to set and use SQL modes in MySQL?

SQL mode is used to control the strictness of MySQL when processing data, affecting the processing of invalid or missing values; 2. You can view the current mode through SELECT@@sql_mode or SHOWVARIABLESLIKE'sql_mode'; 3. Use SETSESSION to set the session-level mode, SETGLOBAL to set the global mode, or set it in the my.cnf/my.ini configuration file to take effect permanently; 4. Common mode combinations include strict mode, MySQL8.0 default mode and unrecommended empty mode; 5. Note that some modes have been deprecated or removed, and loose mode should be avoided in production environments. It is recommended to use strict mode after testing in the development environment to ensure data.

Aug 12, 2025 am 01:23 AM

How to configure the MySQL server

LocateandedittheMySQLconfigurationfile(my.cnformy.ini)basedonyourOS,creatingitifnecessaryandbackingitupbeforechanges.2.Setbasicserversettingsunder[mysqld],includingserver-id,port,bind-address,datadir,socket,character-set-server=utf8mb4,andskip-name-r

Aug 12, 2025 am 01:13 AM

How to choose a partitioning key in MySQL

Choosing a good MySQL partition key is crucial, and the answer is to determine based on query patterns, data distribution, maintenance requirements and key stability. 1. First determine the partition type (such as RANGE is suitable for ordered values, LIST is suitable for discrete categories, HASH and KEY are suitable for uniform distribution), and then select the matching key; 2. Prioritize columns frequently used for WHERE, JOIN or ORDERBY conditions to achieve partition pruning and avoid full partition scanning; 3. Ensure that the data is evenly distributed among each partition and avoid skew (such as most of the status columns are "active" to cause hot spots); 4. If you need to clean up the data by time, select the date column for RANGE partitioning to facilitate the rapid deletion of old partitions; 5. Avoid frequent use

Aug 12, 2025 am 12:17 AM