Basic cursor loop

Emulation context

Basic cursor loops are one of the most common cursor patterns in SQL Server. They involve declaring a simple CURSOR over a query, opening it, and iterating row by row using FETCH NEXT until all rows have been processed.

This pattern is often used when:

• Processing rows in sequential order.
• Applying per-row logic not easily expressed as a set operation.
• Writing administrative or reporting scripts that iterate over small-to-moderate result sets.

However, because Microsoft Fabric Warehouse does not support cursors natively, this imperative, row-wise iteration must be transformed into a Fabric-compatible structure to preserve logic without breaking execution.

Emulation strategy

SQL Tran emulates the basic cursor loop by:

• Converting the cursor’s query into a temporary table that holds the full result set.
• Adding an explicit row number (ROW_NUMBER() window function) to track position.
• Rewriting the loop into a WHILE construct that increments a scalar counter (@CurrentRow) from 1 to the row count.
• Using SELECT statements to retrieve the current row’s data into variables based on the row number.

This approach ensures the per-row processing remains deterministic and compatible with Fabric’s distributed architecture.

Code example

SQL Server:

CREATE PROCEDURE dbo.ProcessPeople
AS
BEGIN
    DECLARE @BusinessEntityID INT, @LastName NVARCHAR(50);
    DECLARE person_cursor CURSOR FOR
    SELECT BusinessEntityID, LastName FROM Person.Person;
    OPEN person_cursor;
    FETCH NEXT FROM person_cursor INTO @BusinessEntityID, @LastName;
    WHILE @@FETCH_STATUS = 0
    BEGIN
        -- Placeholder for logic
        FETCH NEXT FROM person_cursor INTO @BusinessEntityID, @LastName;
    END;
    CLOSE person_cursor;
    DEALLOCATE person_cursor;
END

Fabric Warehouse (generated by SQL Tran):

CREATE PROCEDURE dbo.ProcessPeople
AS
BEGIN
    DECLARE @BusinessEntityID INT, @LastName NVARCHAR(50);
    DECLARE @RowCount_person_cursor INT;
DECLARE @CurrentRow_person_cursor INT = 1;
CREATE TABLE #person_cursor (
	RowNum INT, BusinessEntityID INT, LastName NVARCHAR(50)
)INSERT
	INTO #person_cursor (RowNum, BusinessEntityID, LastName)
	SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNum,
		BusinessEntityID,
		LastName
	FROM
		Person.Person;
SELECT @RowCount_person_cursor = COUNT(*)
FROM
	#person_cursor;
    
    SELECT @BusinessEntityID = BusinessEntityID,
	@LastName = LastName
FROM
	#person_cursor
WHERE
	RowNum = @CurrentRow_person_cursor;
    WHILE @CurrentRow_person_cursor <= @RowCount_person_cursor
    BEGIN
        -- Placeholder for logic
        SET @CurrentRow_person_cursor = @CurrentRow_person_cursor + 1;
SELECT @BusinessEntityID = BusinessEntityID,
	@LastName = LastName
FROM
	#person_cursor
WHERE
	RowNum = @CurrentRow_person_cursor;
    END;
    
    DROP TABLE IF EXISTS #person_cursor;
END

Important notes

• Pre-materialization: The entire result set is materialized into the temporary table before the loop starts. Changes made to the source table after the loop begins are not reflected during iteration.
• Order handling: Since ROW_NUMBER() uses an ORDER BY (SELECT NULL), no explicit order is guaranteed unless the original cursor query includes its own ORDER BY.
• Performance considerations: While this approach works well for small-to-medium result sets, processing large volumes row by row in Fabric may impact performance. Where possible, consider rewriting logic as set-based operations.
• Preserved comments: The translated code preserves any comments from the original source code, ensuring clarity during review.