Hi,
Sorry, I use mysql, not in sqlite, in mysql ,I run this command, the console
show this error: do you know why?
Thank you very much!
mysql> UPDATE adlbk20140520a
-> SET pflopf = (
-> SELECT pflopf
-> FROM adl
-> WHERE adl.ref = adlbk20140520a.ref)
-> WHERE (
-> SELECT COUNT(*)
-> FROM (
-> SELECT 1 FROM adl
-> WHERE adl.ref = adlbk20140520a.ref
-> LIMIT 2
-> )
-> ) = 1;
ERROR 1248 (42000): Every derived table must have its own alias
mysql>
> Message: 8
> Date: Mon, 19 May 2014 09:55:25 +0300
> From: Paul <[email protected]>
> To: [email protected]
> Cc: [email protected]
> Subject: Re: [sqlite] how to write this commands?
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset="UTF-8"
>
>
> > UPDATE adla1
> > SET pflopf = (
> > SELECT pflopf
> > FROM adl
> > WHERE adl.ref = adla1.ref)
> > WHERE (
> > SELECT COUNT(*)
> > FROM (
> > SELECT 1 FROM adl
> > WHERE adl.ref = adla1.ref
> > LIMIT 2
> > )
> > ) = 1;
> >
> > Not all sure what LIMIT 2 does there. I think a SQL-92 version
> > would be
> >
>
> Limit, limits number of rows selected by ref. If we have found 2, no need
> to lookup further.
> That's why it was said to be a slightly optimized version. Generally this
> saves some disk reads.
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