Sometimes, especially if the data is organized in a hierarchical or tree structure, it makes sense to have a procedure call itself. This is known as a recursive call. SQR, unlike most languages, does not have a call stack. So, in order for the recursion to work as expected we have to emulate one in the SQR code itself. It gets even a bit more complicated if we need "begin-select" sections in the recursive procedure. If SQR encounters the "begin-select" line again before the previous cursor is closed it will just fetch the next row. Below are two examples, each with a correct program and one that you might think would work at first glance.
Fibonacci Sequence: Each number is the sum of the two previous numbers. So, the sequence starts: 1,1,2,3,5,8,13,21,34 . . . fib_right.sqr fib_wrong.sqr
Family Tree: This example descends a family tree starting with an ancestor. recurse_right.sqr recurse_wrong.sqr
Source: http://www.ontko.com/sqr/