? Cursor in SQL

A Cursor is a database object used to retrieve, manipulate, and navigate through a result set row-by-row. It allows you to process individual rows returned by a query sequentially.

? Why Use a Cursor?

• When you need to perform row-by-row operations (not set-based).

• Useful in procedural logic within stored procedures or scripts.

• For complex operations where set-based SQL isn’t sufficient.

? Basic Cursor Workflow

1. Declare the cursor with a SELECT statement.

2. Open the cursor to execute the query and populate the result set.

3. Fetch rows one at a time.

4. Process each row as needed.

5. Close the cursor when done.

6. Deallocate (remove) the cursor.

? Example in SQL Server

DECLARE @EmployeeID INT, @EmployeeName VARCHAR(100);DECLARE employee_cursor CURSOR FORSELECT EmployeeID, EmployeeName FROM Employees;OPEN employee_cursor;FETCH NEXT FROM employee_cursor INTO @EmployeeID, @EmployeeName;WHILE @@FETCH_STATUS = 0BEGIN    PRINT 'Employee ID: ' + CAST(@EmployeeID AS VARCHAR) + ', Name: ' + @EmployeeName;    -- Fetch the next row    FETCH NEXT FROM employee_cursor INTO @EmployeeID, @EmployeeName;ENDCLOSE employee_cursor;DEALLOCATE employee_cursor;

? Notes

• Cursors can be slow and resource-intensive; use set-based operations if possible.

• Cursor syntax varies between SQL databases (e.g., SQL Server, Oracle, MySQL).

• MySQL has handlers and loops to simulate cursor behavior inside stored procedures.

If you want, I can provide cursor examples for other databases or explain alternatives to cursors!