SQL Server Alternatives Cursor

As we know, the cursors are required when we need to update records in a database table in singleton fashion means row by row. A Cursor also impacts the performance of the SQL Server since it uses the SQL Server instance’s memory, reduce concurrency, decrease network bandwidth and lock resources.

You should avoid the use of cursor. In this article, I am explaining how you can use cursor alternatives like as WHILE loop, Temporary tables and Table variables. We should use cursor in that case when there is no option except cursor.

Example of Cursor Alternative

Suppose we have table "ProductSales" that stores the information about each product sales. Now we want to calculate the Total Sales Quantity and Amount of each and every product.

We can solve this problem by following three methods.

 CREATE TABLE ProductsSales
(
 ID int IDENTITY(1,1) NOT NULL,
 ProductID int NOT NULL,
 ProductName varchar(50) NOT NULL,
 Qty int NOT NULL,
 Amount decimal(10, 2) NOT NULL ) 
GO
SELECT * FROM ProductsSales
--We have the table with below data 

Problem solution methods

1. Using Cursor

    SET NOCOUNT ON 
   DECLARE @ProductID INT 
   DECLARE @ProductName VARCHAR(100) 
   DECLARE @TotalQty INT 
   DECLARE @Total INT 
   DECLARE @TProductSales TABLE 
   ( 
    SNo INT IDENTITY(1,1),
    ProductID INT,
    ProductName VARCHAR(100),
    TotalQty INT,
    GrandTotal INT
    ) 
   --Declare Cursor 
   DECLARE Cur_Product CURSOR FOR SELECT DISTINCT ProductID FROM ProductsSales
    --Open Cursor 
   OPEN Cur_Product 
   --Fetch Cursor 
   FETCH NEXT FROM Cur_Product INTO @ProductID
   WHILE @@FETCH_STATUS = 0
    BEGIN 
   SELECT @ProductName = ProductName FROM ProductsSales WHERE ProductID = @ProductID 
   SELECT @TotalQty = SUM(Qty),@Total = SUM(Amount) FROM ProductsSales WHERE ProductID = @ProductID 
   INSERT INTO @TProductSales(ProductID,ProductName,TotalQty,GrandTotal) VALUES(@ProductID,@ProductName,@TotalQty,@Total) 
   FETCH NEXT FROM Cur_Product INTO @ProductID END 
   --Close and Deallocate Cursor
    CLOSE Cur_Product 
    DEALLOCATE Cur_Product
    --See Calculated data 
   SELECT * FROM @TProductSales 

   

2. Using Table Variable

    SET NOCOUNT ON 
   DECLARE @ProductID INT 
   DECLARE @ProductName VARCHAR(100) 
   DECLARE @TotalQty INT 
   DECLARE @Total INT 
   DECLARE @i INT =1 
   DECLARE @count INT 
    --Declare Table variables for storing data 
   DECLARE @TProduct TABLE ( SNo INT IDENTITY(1,1),
    ProductID INT
    ) 
    DECLARE @TProductSales TABLE
    (
    SNo INT IDENTITY(1,1),
    ProductID INT,
    ProductName VARCHAR(100),
    TotalQty INT,
    GrandTotal INT
    ) 
    --Insert data to Table variable @Product 
    INSERT INTO @TProduct(ProductID)
    SELECT DISTINCT ProductID FROM ProductsSales ORDER BY ProductID ASC 
    -- Count number of rows
    SELECT @count = COUNT(SNo) FROM @TProduct WHILE (@i <= @count)
    BEGIN
    SELECT @ProductID = ProductID FROM @TProduct WHERE SNo = @i
    SELECT @ProductName = ProductName FROM ProductsSales WHERE ProductID = @ProductID 
    SELECT @TotalQty = SUM(Qty),@Total = SUM(Amount) FROM ProductsSales WHERE ProductID = @ProductID 
    INSERT INTO @TProductSales(ProductID,ProductName,TotalQty,GrandTotal) VALUES(@ProductID,@ProductName,@TotalQty,@Total)
    SELECT @i = @i + 1
    END
    --See Calculated data
    SELECT * FROM @TProductSales 

   

3. Using Temporary Table

    SET NOCOUNT ON 
   DECLARE @ProductID INT 
   DECLARE @ProductName VARCHAR(100) 
   DECLARE @TotalQty INT 
   DECLARE @Total INT 
   DECLARE @i INT =1
   DECLARE @count INT 
   --Create Temporary Tables for storing data 
   CREATE TABLE #TProduct ( SNo INT IDENTITY(1,1),
    ProductID INT
    ) 
    CREATE TABLE #TProductSales
    (
    SNo INT IDENTITY(1,1),
    ProductID INT, ProductName VARCHAR(100), TotalQty INT, GrandTotal INT )
    --Insert data to temporary table #Product 
   INSERT INTO #TProduct(ProductID) SELECT DISTINCT ProductID FROM ProductsSales ORDER BY ProductID ASC 
   SELECT @count = COUNT(SNo) FROM #TProduct 
   WHILE (@i <= @count) 
   BEGIN 
   SELECT @ProductID = ProductID FROM #TProduct WHERE SNo = @i
   SELECT @ProductName = ProductName FROM ProductsSales WHERE ProductID = @ProductID 
   SELECT @TotalQty = SUM(Qty),@Total = SUM(Amount) FROM ProductsSales WHERE ProductID = @ProductID 
   INSERT INTO #TProductSales(ProductID,ProductName,TotalQty,GrandTotal) VALUES(@ProductID,@ProductName,@TotalQty,@Total)
   SELECT @i = @i + 1
    END
    --See Calculated data
    SELECT * FROM #TProductSales 
   --Now Drop Temporary Tables
    DROP TABLE #TProduct
    DROP TABLE #TProductSales 

   

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Summary

In this article, I try to explain the Cursor alternative in SQL Server with simple examples. I hope after reading this article you will be able to use Cursor alternative in SQL Server. I would like to have feedback from my blog readers. Please post your feedback, question, or comments about this article.

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