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Confusion with CTEs

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Topic

max_tm
Starting Member

4 Posts

Posted - 2008-09-10 : 11:09:13

Hi all, just started using SQL Server yesterday. I have a modest programming background but I am having trouble understanding this particular implementation: http://www.devx.com/dbzone/Article/35550/0/page/1
of percentile calculations. My issue is with:

SELECT
CASE
WHEN t1.salary = t2.salary THEN t1.salary
ELSE t1.salary + (t2.salary - t1.salary) * ((@percentile - t1.curr_rank) / (t2.curr_rank - t1.curr_rank))
END
FROM emp_sal t1, emp_sal t2
...

specifically the last line. Intuitively, I understand this as "run through emp_sal and give us something to refer to it" (in this case t1 and t2). My question is, why do two consecutive applications of emp_sal produce different results? Am I missing something very important about CTEs here