How to use the DATE_FORMAT function in MySQL to convert a date into a string in a specified format

MySQL supports CHECK constraints to force domain integrity, effective from version 8.0.16; 1. Add constraints when creating a table: Use CREATETABLE to define CHECK conditions, such as age ≥18, salary > 0, department limit values; 2. Modify the table to add constraints: Use ALTERTABLEADDCONSTRAINT to limit field values, such as name non-empty; 3. Use complex conditions: support multi-column logic and expressions, such as end date ≥start date and completion status must have an end date; 4. Delete constraints: use ALTERTABLEDROPCONSTRAINT to specify the name to delete; 5. Notes: MySQL8.0.16, InnoDB or MyISAM needs to be quoted

When dealing with large tables, MySQL performance and maintainability face challenges, and it is necessary to start from structural design, index optimization, table sub-table strategy, etc. 1. Reasonably design primary keys and indexes: It is recommended to use self-increment integers as primary keys to reduce page splits; use overlay indexes to improve query efficiency; regularly analyze slow query logs and delete invalid indexes. 2. Rational use of partition tables: partition according to time range and other strategies to improve query and maintenance efficiency, but attention should be paid to partitioning and cutting issues. 3. Consider reading and writing separation and library separation: Read and writing separation alleviates the pressure on the main library. The library separation and table separation are suitable for scenarios with a large amount of data. It is recommended to use middleware and evaluate transaction and cross-store query problems. Early planning and continuous optimization are the key.

The core methods for realizing MySQL data blood ties tracking include: 1. Use Binlog to record the data change source, enable and analyze binlog, and trace specific business actions in combination with the application layer context; 2. Inject blood ties tags into the ETL process, and record the mapping relationship between the source and the target when synchronizing the tool; 3. Add comments and metadata tags to the data, explain the field source when building the table, and connect to the metadata management system to form a visual map; 4. Pay attention to primary key consistency, avoid excessive dependence on SQL analysis, version control data model changes, and regularly check blood ties data to ensure accurate and reliable blood ties tracking.

Check whether the MySQL service is running, use sudosystemctlstatusmysql to confirm and start; 2. Make sure that bind-address is set to 0.0.0.0 to allow remote connections and restart the service; 3. Verify whether the 3306 port is open, check and configure the firewall rules to allow the port; 4. For the "Accessdenied" error, you need to check the user name, password and host name, and then log in to MySQL and query the mysql.user table to confirm permissions. If necessary, create or update the user and authorize it, such as using 'your_user'@'%'; 5. If authentication is lost due to caching_sha2_password

Useamany-to-manyrelationshipwithajunctiontabletolinkitemsandtagsviathreetables:items,tags,anditem_tags.2.Whenaddingtags,checkforexistingtagsinthetagstable,insertifnecessary,thencreatemappingsinitem_tagsusingtransactionsforconsistency.3.Queryitemsbyta

DELETEremovesspecificorallrows,keepstablestructure,allowsrollbackandtriggers,anddoesnotresetauto-increment;2.TRUNCATEquicklyremovesallrows,resetsauto-increment,cannotberolledbackinmostcases,doesnotfiretriggers,andkeepstablestructure;3.DROPremovesthee

CheckcompatibilitywithOS,applications,andfeatures;2.Backupalldata,configs,andlogs;3.Chooseupgrademethod(packagemanager,MySQLInstaller,ormanual);4.Runpost-upgradechecksandtests;5.Resolveissueslikeauthenticationpluginsordeprecatedoptions.Alwaysbackup,t

Using mysqldump is the most common and effective way to back up MySQL databases. It can generate SQL scripts containing table structure and data. 1. The basic syntax is: mysqldump-u[user name]-p[database name]>backup_file.sql. After execution, enter the password to generate a backup file. 2. Back up multiple databases with --databases option: mysqldump-uroot-p--databasesdb1db2>multiple_dbs_backup.sql. 3. Back up all databases with --all-databases: mysqldump-uroot-p