SQL Server Cursors
Duration : 00:01:00
Transact-SQL Cursors
Transact-SQL (T-SQL) cursors are used in SQL Server to iterate through result sets row by row. They provide fine-grained control over data manipulation and retrieval.Example
DECLARE @EmployeeName NVARCHAR(50)
DECLARE cursor_employee CURSOR FOR
SELECT EmployeeName FROM Employees
OPEN cursor_employee
FETCH NEXT FROM cursor_employee INTO @EmployeeName
WHILE @@FETCH_STATUS = 0
BEGIN
PRINT @EmployeeName
FETCH NEXT FROM cursor_employee INTO @EmployeeName
END
CLOSE cursor_employee
DEALLOCATE cursor_employee
Client Cursors
Client cursors are cursors that are managed on the client-side, where the client application is responsible for cursor control and data retrieval.Forward-only Cursor
Suitable for one-time read-only traversal of result sets.Example
DECLARE cursor_forward CURSOR FORWARD_ONLY FOR
SELECT ProductName FROM Products
Static Cursor
Represents a snapshot of data, and changes made by other users aren't visible.Example
DECLARE cursor_static CURSOR STATIC FOR
SELECT CustomerName FROM Customers
Keyset Cursor
Holds a unique identifier for each row, making it useful when you need to scroll through data efficiently.Example
DECLARE cursor_keyset CURSOR KEYSET FOR
SELECT OrderID FROM Orders
Dynamic Cursor
Reflects all data changes made by other users during cursor navigation.Example
DECLARE cursor_dynamic CURSOR DYNAMIC FOR
SELECT SalesAmount FROM SalesData
Requesting a Cursor
To request a cursor in SQL Server, you typically use the DECLARE CURSOR statement followed by the cursor definition and data retrieval queries.Example
DECLARE cursor_example CURSOR FOR
SELECT ProductName, UnitPrice FROM Products
Cursor Process
The process of using a cursor in SQL Server typically involves declaring the cursor, opening it, fetching rows one by one, and then closing and deallocating the cursor.Example
DECLARE cursor_process CURSOR FOR
SELECT CustomerName, OrderAmount FROM Orders
OPEN cursor_process
FETCH NEXT FROM cursor_process INTO @CustomerName, @OrderAmount
WHILE @@FETCH_STATUS = 0
BEGIN
-- Process data here
FETCH NEXT FROM cursor_process INTO @CustomerName, @OrderAmount
END
CLOSE cursor_process
DEALLOCATE cursor_process
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