Examples explaining how to use functions 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

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

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.

Thelistener.orafileisessentialforconfiguringtheOracleNetListenertoacceptandrouteclientconnectionrequests;itdefineslisteningaddressesandports,specifiesdatabaseservicesviastaticregistration,andsetslistenerparameterslikeloggingandtracing;locatedin$ORACL

OracleSQL's CASE statement is used to implement conditional logic in queries, supporting two forms: 1. Simple CASE is used to compare a single expression with multiple values, such as returning department names according to department_id; 2. Search CASE is used to evaluate multiple boolean conditions, suitable for scope or complex logic, such as classified by salary level; 3. CASE can be used in SELECT, ORDERBY, WHERE (indirect), GROUPBY and HAVING clauses to implement data conversion, sorting, filtering, and grouping; 4. Best practices include always using ELSE to prevent NULL, ensure ending in END, adding alias to the result columns, and avoiding excessive nesting; 5. Compared with the old DECOD

To find the size of an Oracle table, you need to query the size of its related segments. The specific steps are as follows: 1. Use the USER_SEGMENTS or DBA_SEGMENTS view to get the size of the table and its related objects, execute the SELECT statement and replace the table name in capital form to get the size in MB; 2. By grouping the query by segment_type, you can view the size of the table data, index and LOB segments respectively; 3. To obtain the total space occupation of the table and all related objects (including index and LOB), you need to jointly query the segment names in user_segments, user_indexes and user_lobs; 4. If you only need the table data size, you can add it in the query

Usethe||operatortoconcatenatemultiplecolumnsinOracle,asitismorepracticalandflexiblethanCONCAT();2.Addseparatorslikespacesorcommasdirectlywithintheexpressionusingquotes;3.HandleNULLvaluessafelysinceOracletreatsthemasemptystringsduringconcatenation;4.U

The structure of PL/SQL block mainly includes four parts: DECLARE, BEGIN, EXCEPTION and END. 1.DECLARE is an optional part, used to declare variables, constants, cursors and user-defined types, and all declarations must be before the BEGIN keyword; 2.BEGIN is a required part, containing execution logic, such as SQL statements, control structures and function calls, which are where the actual work is completed; 3.EXCEPTION is an optional error handling part, used to handle runtime errors, and supports specific exceptions (such as NO_DATA_FOUND) and general exceptions (WHENOTHERSTHEN); 4.END marks the end of the block, and each PL/SQL block must be