AW: Access-Daten in Mysql-DB

["Michael Donning" <donning_(at)_informenta.de>]

Hallo Olli,

>...
> Ich moechte an folgender, beispielhafter Tabelle
>
> router ; frames_sent ; time_stamp
>
> zu jedem router die max(frames_sent) *mit* Angabe des dazugehoerigen
> time_stamp haben.
> ...

kann man fast als RTFM Frage bezeichnen. Schau Dir doch mal das
untenstehende Beispiel aus dem Handbuch an.

9.3.4 The Rows Holding the Group-wise Maximum of a CertainField
For each article, find the dealer(s) with the most expensive price."
...
In MySQL it's best do it in several steps:
1. Get the list of (article,maxprice).
2. For each article get the corresponding rows that have the stored maximum
price.
This can easily be done with a temporary table:

CREATE TEMPORARY TABLE tmp (
article INT(4) UNSIGNED ZEROFILL DEFAULT '0000' NOT NULL,
price DOUBLE(16,2) DEFAULT '0.00' NOT NULL);

LOCK TABLES shop read;

INSERT INTO tmp SELECT article, MAX(price) FROM shop GROUP BY article;

SELECT shop.article, dealer, price FROM shop, tmp
WHERE shop.article=tmp.article AND shop.price=tmp.price;

UNLOCK TABLES;

DROP TABLE tmp;

Gruss, Michael

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