FORWARD_ONLY Cursor in SQL Server

The FORWARD_ONLY Cursor in SQL Server does not support scrolling. This cursor can only move from first row to last, and does not support the other way (scrolling backwards). It means, FORWARD_ONLY Cursors support FETCH_ONLY option, and it will an error for all the remaining FETCH options.

SQL Server allows us to use the STATIC, DYNAMIC, or KEYSET keywords along with the FORWARD_ONLY Cursor. And if you omit any of these keywords then SQL assumes it as DYNAMIC. In this article we will show you, How to Create a forward_only Cursor in SQL Server with example. For this demonstration, We are going to use the below shown table. As you can see from the below screenshot that our Employee table hold 14 records

Forward_Only Cursor in SQL Server Example 1

In this example we will show you, How to declare, and open a forward_only cursor in SQL Server. And here, we will use the different FETCH option to demonstrate the supporting fetch options.

T-SQL CODE

USE [SQL Tutorial]
GO

DECLARE forward_employee_cursor CURSOR FORWARD_ONLY
    FOR SELECT * FROM [EmployeeTable]
OPEN forward_employee_cursor  
FETCH NEXT FROM forward_employee_cursor;

ANALYSIS

Below statement will declare the forward_only cursor called forward_employee_cursor for all the records in Employee table

DECLARE forward_employee_cursor CURSOR FORWARD_ONLY
    FOR SELECT * FROM [EmployeeTable]

Below statement will open the declared cursor

OPEN forward_employee_cursor

Next statement will fetch, or return the next record from the forward_employee_cursor cursor.

FETCH NEXT FROM forward_employee_cursor;

OUTPUT

Though our employee table has 14 records, the cursor is retrieving 1 record. This is because, FETCH NEXT will fetch only one record from the cursor, and if you want all then use Loops.

Let me use the FETCH FIRST option. As you can see, this is throwing an error.

Let me use the FETCH LAST option.

Next, we used the FETCH PRIOR option.

Forward_Only Cursor in SQL Server example 2

In this example we will show you, How to create FORWARD_ONLY STATIC Cursors, and FORWARD_ONLY DYNAMIC Cursors. For this, we are using the DECLARE CURSOR Statement, and within that, we will use the WHILE LOOP to loop over the cursor elements, and perform updates

T-SQL CODE

SET NOCOUNT ON
-- Declaring the Variables 
DECLARE @EmpID INT,
        @EmpName VARCHAR(50),
        @EmpEducation VARCHAR(50),
	@EmpOccupation VARCHAR(50),
	@EmpYearlyIncome DECIMAL (10, 2), 
	@EmpSales DECIMAL (10, 2);

DECLARE forward_employee_cursor CURSOR 
FORWARD_ONLY STATIC FOR 
	SELECT [ID]
	      ,[Name]
	      ,[Education]
	      ,[Occupation]
	      ,[YearlyIncome]
	      ,[Sales]
	FROM EmployeeTable
        ORDER BY Occupation

OPEN forward_employee_cursor
IF @@CURSOR_ROWS > 0
BEGIN 
      FETCH NEXT FROM forward_employee_cursor
            INTO @EmpID, @EmpName, @EmpEducation,
	         @EmpOccupation, @EmpYearlyIncome, @EmpSales
      WHILE @@FETCH_STATUS = 0
      BEGIN
	IF @EmpOccupation = N'Management'
 	    UPDATE [EmployeeTable] 
		SET [YearlyIncome] = 999999,
		    [Sales] = 15000
	    WHERE CURRENT OF forward_employee_cursor                
		
        FETCH NEXT FROM forward_employee_cursor
             INTO @EmpID, @EmpName, @EmpEducation,
	          @EmpOccupation, @EmpYearlyIncome, @EmpSales
      END
END
CLOSE forward_employee_cursor
DEALLOCATE forward_employee_cursor
SET NOCOUNT OFF 
GO

OUTPUT

If you observe the cursor declaration carefully, we are using FORWARD_ONLY STATIC cursor, and performing the UPDATE option. We already explained the remaining steps in our previous article, I suggest you to refer Dynamic Cursor in SQL Server example.

You can see that, the error is stating : The Cursor is READ ONLY. This is because, we mentioned the FORWARD_ONLY STATIC in the cursor declaration. And, STATIC Cursors doe not support INSERT, DELETE, or UPDATE operations.

Please use the following SQL Query to check whether the Cursor has updated any of the records in Employee table or not.

T-SQL CODE

USE [SQL Tutorial]
GO
SELECT [ID]
      ,[Name]
      ,[Education]
      ,[Occupation]
      ,[YearlyIncome]
      ,[Sales]
  FROM [EmployeeTable]

OUTPUT

Let me change the cursor declaration from static to dynamic by writing : FORWARD_ONLY DYNAMIC. Remember, it will work even if you forgot the DYNAMIC keyword because it is the default keyword for the forward_only trigger

Now you can see the updated records.

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