<pre>
mysql> select max(dh.maxtid),max(d.tiden) from heaptest dh,diary d;
+---------------------+---------------------+
| max(dh.maxtid) | max(d.tiden) |
+---------------------+---------------------+
| 2002-04-02 13:01:52 | 2002-04-02 13:01:52 |
+---------------------+---------------------+
1 row in set (53.42 sec)
mysql> select max(tiden) from diary;
+---------------------+
| max(tiden) |
+---------------------+
| 2002-04-02 13:01:52 |
+---------------------+
1 row in set (0.34 sec)
mysql> select max(maxtid) from heaptest;
+---------------------+
| max(maxtid) |
+---------------------+
| 2002-04-02 13:01:52 |
+---------------------+
1 row in set (0.00 sec)
mysql>
</pre>
take a look at the accestimes. i wonder why the first sql-query took
so much longer time than the two following.
the first query does exactly the same thing as the two others, but in
only one query.
FYI: the table "heaptest" is a temporary table (type=heap) and both
tables are indexed on "tiden" respectively "maxtid". (and the table
diary contains quite a lot of data).
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