SQL basic query question

Question

I'll be the first one to admit my SQL skills are lacking. Now...

Let's say we've got a database table called Posts with three columns: Id, RootId, and DateTime.

What I'd like to do is get the last (by DateTime) 20 distinct RootId values.

Here's the caveat though: RootId may be NULL, in which case we should consider that record as distinct, and instead of NULL, Id should be returned.

What would the query be?

YogoZuno · Accepted Answer · 2009-07-20 00:15:08Z

2

select distinct top 20 isnull(rootid,id) from posts order by datetime desc

Assuming this is for MS SQL Server

answered Jul 20, 2009 at 0:15

YogoZuno

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2 Comments

isnull(rootid,id) seems a bit odd. Why not isnull(rootid,0)?

Can you offer any ideas how I can take my request and translate it, mentally, into a query? You're correct in your answer.