How to use oracle cursor

Oracle cursor is a database pointer used to traverse a record set, and its features include record-by-record processing, efficiency, updating, and security. Use scenarios include batch processing of data, updating or deleting specific records and transactions.

Oracle Cursor Use

Oracle cursor is a database object used to traverse records in a dataset. It is a database pointer that refers to a result set in the database. Cursors enable developers to process data records one by one, rather than searching the entire result set at once.

How cursors work:

1. Declare cursor: Use the DECLARE statement to declare a cursor and specify the query to be returned.
2. Open cursor: Open cursor with the OPEN statement, it will execute and return the result of the query.
3. Get record: Use the FETCH statement to get the record currently pointed to by the cursor.
4. Processing records: Processing acquired records, such as displaying, modifying, or saving to another data source.
5. Close cursor: Use the CLOSE statement to close the cursor and release the resources it occupies.

Cursor features:

• Record-by-record processing: Cursors allow developers to traverse the result sets record by record, rather than searching all records at once.
• Improved Efficiency: For large result sets, using cursors can improve efficiency because it processes only one record at a time, reducing memory and network overhead.
• Updateability: Some cursors are updating, which means developers can modify records after they get them.
• Security: Cursors can be used to control access to sensitive data because they can only access the records currently pointed to, rather than the entire result set.

Cursor usage scenarios:

• Process large result sets line by line
• Process data in batches
• Update or delete specific records
• Keep locked to specific data
• Implement transaction processing

Example:

 <code>-- 声明一个游标DECLARE cursor_name CURSOR FOR SELECT * FROM table_name; -- 打开游标OPEN cursor_name; -- 逐个记录获取结果FETCH cursor_name INTO variable1, variable2; -- 处理获取到的记录-- ... -- 关闭游标CLOSE cursor_name;</code>

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