SQL Cursor

A SQL cursor is a special kind of object that allows you to iterate over the rows of a result set one by one. You can use a cursor when you need to perform complex logic on each row or when you need to access multiple rows at the same time. To use a cursor, you need to declare it, open it, fetch data from it, and close it.

To declare a cursor, you need to specify a name and a query that defines the result set. For example:

DECLARE product_cursor CURSOR FOR

SELECT name, price FROM products;

To open a cursor, you need to use the OPEN statement. This will execute the query and store the result set in memory. For example:

OPEN product_cursor;

To fetch data from a cursor, you need to use the FETCH statement. This will retrieve the next row from the result set and assign it to some variables. You can also use a loop to fetch all rows until there are no more rows left. For example:

FETCH product_cursor INTO @product_name, @product_price;

WHILE @@FETCH_STATUS = 0

BEGIN

  -- Do something with @product_name and @product_price

  FETCH product_cursor INTO @product_name, @product_price;

END

To close a cursor, you need to use the CLOSE statement. This will release the memory used by the result set. You can also use the DEALLOCATE statement to remove the cursor definition. For example:

CLOSE product_cursor;

DEALLOCATE product_cursor;