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Ordering items by hierarchy without RBAR


Ordering items by hierarchy without RBAR

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kramaswamy
kramaswamy
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Group: General Forum Members
Points: 859 Visits: 1788
Hey all,

I feel like I already know the answer to this question, but it is eluding me ...

Say I have a table with two columns - ID and ParentID. Say this table has the following values:

ID ParentID
10 50
20 30
30 10
50 NULL

Now, say I want the following output from my query:

ID ParentID Order
10 50 2
20 30 4
30 10 3
50 NULL 1

Is there any way to get this result in a single query, without needing potentially infinite recursion or using a row-by-row comparaison?
Jeff Moden
Jeff Moden
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Group: General Forum Members
Points: 45066 Visits: 39904
Sure... you could do a 4 way self join but that's hardcoding levels.

Recursion isn't so bad here. It will do things by level, not by row.

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
Although they tell us that they want it real bad, our primary goal is to ensure that we dont actually give it to them that way.
Although change is inevitable, change for the better is not.
Just because you can do something in PowerShell, doesnt mean you should. Wink

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