SQL Server › Cursors

How would you rewrite a common cursor based row by row update into an equivalent, much faster set based UPDATE statement?

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Answer

You identify the specific logic being applied to each row inside the cursor's loop, and translate that same logic directly into a single UPDATE statement with an appropriate WHERE clause or JOIN, letting SQL Server's query engine apply the change to every matching row at once instead of looping through them individually.

-- Cursor based approach (slow)
-- Loops through each product, updating price one at a time

-- Set based equivalent (fast)
UPDATE Products
SET Price = Price * 1.1
WHERE Category = 'Electronics';

Real-world example A team replaces a slow cursor that increased electronics prices by ten percent one row at a time with a single set based UPDATE statement, cutting the operation's runtime from several minutes down to under a second.

Common follow-ups: What situations genuinely require row by row processing that cannot be converted to a set based operation?;How do you measure the actual performance difference between a cursor and its set based equivalent?

Query Optimization & Plans;Stored Procedures & Functions