What is the use of a cursor in SQL Server?

Cursors are a mechanism to explicitly enumerate through the rows of a result set, rather than retrieving it as such.

However, while they may be more comfortable to use for programmers accustomed to writing While Not RS.EOF Do ..., they are typically a thing to be avoided within SQL Server stored procedures if at all possible -- if you can write a query without the use of cursors, you give the optimizer a much better chance to find a fast way to implement it.

In all honesty, I've never found a realistic use case for a cursor that couldn't be avoided, with the exception of a few administrative tasks such as looping over all indexes in the catalog and rebuilding them. I suppose they might have some uses in report generation or mail merges, but it's probably more efficient to do the cursor-like work in an application that talks to the database, letting the database engine do what it does best -- set manipulation.

Comments

[Spyros Ponaris]

Thanks for sharing.. To be honest, it has been many years since I last used cursors in SQL Server. Instead, I use @@ROWCOUNT to implement loops. Working with cursors can sometimes be dangerous and requires a lot of attention.
Cursors in SQL Server can be resource-intensive and are generally less efficient compared to set-based operations or alternatives like @@ROWCOUNT for looping.

[Clever Cottonmouth]

That makes sense! Cursors can be tricky and can impact performance if not handled properly. Using @@ROWCOUNT for loops is a great alternative in many cases. Recently, I used a cursor in my project to loop through data and store it in the database. In some scenarios, it felt like the best approach. Have you ever encountered a situation where a cursor was unavoidable?

[Spyros Ponaris]

That's a great question! To be honest, I don't use cursors anymore. Instead, I usually fetch the data into an in-memory table and use @@ROWCOUNT in a loop to process the rows.

-- Create temporary table
CREATE TABLE #ProductsTemp (ProductID INT PRIMARY KEY);

-- Insert sample data
INSERT INTO #ProductsTemp VALUES (1), (2), (3);

-- Declare variable
DECLARE @ProductID INT;

-- Loop through rows
WHILE EXISTS (SELECT 1 FROM #ProductsTemp)
BEGIN
-- Fetch the first ProductID
SELECT TOP 1 @ProductID = ProductID FROM #ProductsTemp;

DELETE FROM #ProductsTemp WHERE ProductID = @ProductID;

END;

DROP TABLE #ProductsTemp;

Using this approach, I avoid the overhead of cursors while still maintaining row-by-row control.