用于监控数据库情况
Oracle,需要配置ACL(转自csdn:罗友谋) 无
Oracle , 需要配置ACL(转自csdn:罗友谋)
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MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.

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.

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.

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.

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.

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.
