Uses of Cursors:
- Row-by-Row Processing: Cursors are beneficial when you need to process data row by row, applying complex logic or calculations.
- Data Navigation: Cursors provide a way to navigate through query results, especially when the order of processing is crucial.
- Data Modification: Cursors allow for updating, deleting, or inserting data row by row based on specific conditions.
- Complex Business Logic: When dealing with complex business rules that require iterative processing, cursors can be handy.
Benefits of Cursors:
- Control: Cursors offer precise control over data manipulation operations, allowing for customized processing.
- Flexibility: They provide flexibility in handling data, especially when dealing with non-standard requirements.
- Iterative Processing: Cursors facilitate iterative processing, which is not easily achievable with set-based operations.
- Data Integrity: Cursors help maintain data integrity by allowing for fine-grained manipulation and validation.
Different Keywords for Cursors:
In SQL, there are several keywords associated with cursors:
- DECLARE CURSOR: Used to define a cursor and specify the query to retrieve data.
- OPEN: Opens the cursor and fetches the first row from the result set.
- FETCH: Retrieves the next row from the result set.
- CLOSE: Releases the cursor and the associated resources.
- DEALLOCATE: Removes the cursor definition and releases resources associated with the cursor.
-- Example of using a cursor in SQL
DECLARE cursor_name CURSOR FOR
SELECT column1, column2
FROM table_name;
OPEN cursor_name;
FETCH NEXT FROM cursor_name INTO @var1, @var2;
WHILE @@FETCH_STATUS = 0
BEGIN
-- Process data
FETCH NEXT FROM cursor_name INTO @var1, @var2;
END
CLOSE cursor_name;
DEALLOCATE cursor_name;