Detailed explanation of Oracle version query method

The method to solve the Oracle cursor closure problem includes: explicitly closing the cursor using the CLOSE statement. Declare the cursor in the FOR UPDATE clause so that it automatically closes after the scope is ended. Declare the cursor in the USING clause so that it automatically closes when the associated PL/SQL variable is closed. Use exception handling to ensure that the cursor is closed in any exception situation. Use the connection pool to automatically close the cursor. Disable automatic submission and delay cursor closing.

SQL statements can be created and executed based on runtime input by using Oracle's dynamic SQL. The steps include: preparing an empty string variable to store dynamically generated SQL statements. Use the EXECUTE IMMEDIATE or PREPARE statement to compile and execute dynamic SQL statements. Use bind variable to pass user input or other dynamic values ​​to dynamic SQL. Use EXECUTE IMMEDIATE or EXECUTE to execute dynamic SQL statements.

In Oracle, the FOR LOOP loop can create cursors dynamically. The steps are: 1. Define the cursor type; 2. Create the loop; 3. Create the cursor dynamically; 4. Execute the cursor; 5. Close the cursor. Example: A cursor can be created cycle-by-circuit to display the names and salaries of the top 10 employees.

Deleting all data in Oracle requires the following steps: 1. Establish a connection; 2. Disable foreign key constraints; 3. Delete table data; 4. Submit transactions; 5. Enable foreign key constraints (optional). Be sure to back up the database before execution to prevent data loss.

Solutions to Oracle cannot be opened include: 1. Start the database service; 2. Start the listener; 3. Check port conflicts; 4. Set environment variables correctly; 5. Make sure the firewall or antivirus software does not block the connection; 6. Check whether the server is closed; 7. Use RMAN to recover corrupt files; 8. Check whether the TNS service name is correct; 9. Check network connection; 10. Reinstall Oracle software.

Oracle database paging uses ROWNUM pseudo-columns or FETCH statements to implement: ROWNUM pseudo-columns are used to filter results by row numbers and are suitable for complex queries. The FETCH statement is used to get the specified number of first rows and is suitable for simple queries.

An AWR report is a report that displays database performance and activity snapshots. The interpretation steps include: identifying the date and time of the activity snapshot. View an overview of activities and resource consumption. Analyze session activities to find session types, resource consumption, and waiting events. Find potential performance bottlenecks such as slow SQL statements, resource contention, and I/O issues. View waiting events, identify and resolve them for performance. Analyze latch and memory usage patterns to identify memory issues that are causing performance issues.

Triggers in Oracle are stored procedures used to automatically perform operations after a specific event (insert, update, or delete). They are used in a variety of scenarios, including data verification, auditing, and data maintenance. When creating a trigger, you need to specify the trigger name, association table, trigger event, and trigger time. There are two types of triggers: the BEFORE trigger is fired before the operation, and the AFTER trigger is fired after the operation. For example, the BEFORE INSERT trigger ensures that the age column of the inserted row is not negative.