Help with a WHERE on a LEFT JOIN SQL Query

Question

I\'m trying to construct a query that will include a column indicating whether or not a user has downloaded a document. I have a table called HasDownloaded with the followin

Answer 1

@Mark: I understand why the JOIN syntax works, but thanks for the warning. I do think your suggestion is more intuitive. I was curious to see which was more efficient. So I ran a quick test (this was rather simplistic, I'm afraid, over only 14 rows and 10 trials):

In the JOIN condition:

AND HasDownloaded.memberID = @memberID

• Client processing time: 4.6
• Total execution time: 35.5
• Wait time on server replies: 30.9

In the WHERE clause:

WHERE HasDownloaded.memberId IS NULL OR HasDownloaded.memberId = @memberId

• Client processing time: 7.7
• Total execution time: 27.7
• Wait time on server replies: 22.0

It looks like the WHERE clause is ever-so-slightly more efficient. Interesting! Once again, thanks to both of you for your help.