Re: Querying a database for 50 users' information: 50 queries or a WHERE array?

On Tue, Sep 13, 2011 at 23:04, Alex Nikitin <niksoft@gmail.com> wrote: > Dotan, > > IN (the function used in all of the queries above) is not the same as an > INNER_JOIN, inner join joins 2 tables, as you have already described, IN > however is a function that return 1 if the value being searched for is in > the array of its values or 0 if it is not, thus IN is not an inner join, but > a comparator function, thus if you are using IN, limit will indeed be more > efficient than it's omission for exactly the reason i have stated in my > previous post. Because your user array seems to be in php, and implode has > been a topic of discussion above as well, setting an adequate limit is a > simple task with the php's count function. > Yes, I did realize that after seeing the syntax of IN, which I have not been exposed to before. My response that you quoted was in response to a suggestion that a LIMIT clause be used with an INNER JOIN query, which is wrong on two principles. > This is all ofcourse void if the user array being pulled from mysql, in > which case you could simply join the two tables to get your resulting data > set. The trick there is to use the USING clause which seems to run a lot > faster than any ON clause, or work on an optimized subselect, especially if > you are running a cluster. > Agreed. In fact I don't know from where the array is coming, that's not my part of the code! But I agree that if it is coming from mysql then a join would be preferable. -- Dotan Cohen http://gibberish.co.il http://what-is-what.com