I never understood this: in web development whe[n|re] does it make sense to fetch results one by one?
I mean, why should I use PDOStatement->fetch*() when I can use PDOStatement->fetchAll()?
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23answers:
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A:
fetchAll() will fetch all the results into one big array.
With very large result sets, it could exceed the PHP script's memory limit.
A pure fetch() will fetch each record one by one, neutralizing that danger.
That's the only reason not to use fetchAll() I can think of.
Pekka
2010-05-09 10:42:06
Sure, but we usually don't emit SQL statements like `SELECT * FROM oneMillionRowsTable` without a limit clause, at least I've never seen a query like that in web applications.
Alix Axel
2010-05-09 10:45:57
@Alix neither have I, but it is not entirely unthinkable to happen. I prefer the `fetch` variant out of a general sense of "My PHP script's memory is more limited than that of the mySQL server". It could be, though, that `fetchAll` is faster because it talks to the server only once - I don't know, I've never measured it.
Pekka
2010-05-09 10:48:13
Thanks Pekka. =)
Alix Axel
2010-05-09 10:49:54