How to change username in oracle

Run SELECT*FROMv$version; you can obtain the complete version information of the Oracle database, including the database, PL/SQL, core library, etc. version details, which is the most commonly used reliable method for DBA; 2. Use SELECTbannerFROMv$versionWHEREbannerLIKE'Oracle%'; you can only display the main version information of the Oracle database; 3. Query the PRODUCT_COMPONENT_VERSION view to get the version of each Oracle component; 4. Through the sqlplus-V command, you can view the client or server tool version without logging into the database, but it may not reflect the actual running

Oracle deadlock occurs when two or more sessions wait for each other to release resource locks, forming a circular dependency. For example: 1. After session A updates line 1, try to update line 2; 2. After session B updates line 2, try to update line 1. If it runs at the same time, it will block each other to form a deadlock. Oracle automatically detects and rolls back one of the transactions to break the deadlock, which receives an ORA-00060 error. Other common reasons include not committing transactions holding row-level locks, improper index usage causes lock upgrades, and application logic allows out-of-order overlapping updates. The detection methods include viewing deadlock records in the alert log, tracking files, and querying V$LOCKED_OBJECT and V$SESSION views. The solution is to analyze and track files and ensure transactions

BULKCOLLECT and FORALL significantly improve PL/SQL performance by reducing context switching. 1. BULKCOLLECT batch-in-batch data to the set at one time to avoid frequent switching caused by line-by-line acquisition; 2. FORALL sends the DML operations of the set to the SQL engine for processing at one time, replacing inefficient loop execution one by one; 3. The combination of the two can realize efficient data extraction, processing and update, and is suitable for ETL, batch tasks and other scenarios; 4. When using it, pay attention to controlling the set size, rationally use LIMIT batch processing, and avoid adding complex conditional logic to FORALL.

InOracle’slogicalstoragehierarchy,segments,extents,andblocksformastructuredframeworkfordatastorage.Datablocksarethesmalleststorageunit,typically8KBinsize,whereactualdataliketablerowsorindexentriesarestored.Extentsconsistofcontiguousdatablocksallocate

TheOracleOptimizerdeterminesthemostefficientwaytoexecuteSQLbyanalyzingexecutionplansbasedonstatisticsandcostestimation.1.Itdecideshowtoaccessdata,includingindexusage,tablejoinorder,andjoinmethods.2.Itestimatescostusingtableandsystemstatistics,andpred

OraclesupportsJSONdatatypesandoperationssinceOracle12c,enablingefficientstorage,querying,andmanipulationofsemi-structureddatawithinarelationalSQLenvironment.1.JSONdataisstoredusingVARCHAR2,CLOB,orBLOBtypeswithacheckconstraint(ISJSON)toensurevalidity.

Connect to users with DBA permissions; 2. Use the CREATEUSER command to create users and specify necessary parameters; 3. Grant system permissions such as CREATESSION, CREATETABLE, etc. or use CONNECT and RESOURCE roles; 4. Grant additional permissions such as CREATEPROCEDURE or UNLIMITEDTABLESPACE as needed; 5. Optionally grant object permissions to other user objects; 6. Verify user login, the entire process needs to ensure that it is executed in the correct container and follow the principle of minimum permissions, use a strong password policy, and finally complete Oracle user creation and permission allocation.

Oraclesequences and identitycolumns can generate self-value-added, but the mechanism is different from the applicable scenarios. 1. Oracle sequences are independent objects that can be used across tables, providing higher control flexibility, such as cache, looping, etc.; 2. The Identity column embeds the self-increment logic in the table column, simplifying the settings, suitable for simple scenarios and closer to MySQL/PostgreSQL usage; 3. The key differences are the scope of action (sequences are available globally, identity columns are limited to single tables), control ability (sequence functions are stronger) and ease of use (identity columns are more intuitive); 4. It is recommended to use identity columns in simple scenarios, and when complex systems or shared counters are required, the sequence is preferred.