Re: psql with PHP question
От | Gyozo Papp |
---|---|
Тема | Re: psql with PHP question |
Дата | |
Msg-id | 01b001c0d569$b3513560$4647c5d5@jaguar обсуждение исходный текст |
Ответ на | Re: psql with PHP question (Jesus Aneiros <aneiros@ucfinfo.ucf.edu.cu>) |
Список | pgsql-php |
Hello, just some more word : > > In my opinion, these queries make the same : > > SELECT id FROM article WHERE id=(SELECT MAX(id) FROM article); > > SELECT MAX(id) FROM article; > > > > but the latter one is much more simple and you do not overload your pg. > > (by the way, I think id = (SELECT ...) isn't handled gracefully.) > > Hi, although I agreee with the first part: the subselect is redundat in > this case, I don't understand de second one. The subselect will return one > value, or am I wrong? So, I think the operator = will be correct, or not? I mean the second sentence that I don't think the planner/optimizer is so clever to reduce the former query to the latterone. You're right the sublselect will return one value, but as far as I know this value should be interpreted as a set of onevalue (because of the select). ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)
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