Re: Double Index Performance

[Björn Steinbrink]

What about this?
SELECT MAX(PostDate) FROM Person_Test WHERE PersonId = 1

Even simpler (IMHO) and EXPLAIN agrees on performance:
mysql> explain SELECT MAX(PostDate) FROM Person_Test where PersonId=1;
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
| 1 | SIMPLE | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Select tables optimized away |
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
1 row in set (0.00 sec)