mysql> explain SELECT COUNT( DISTINCT p.bsg_uk ) AS act_mbr
    -> FROM bsgtran.pre p, bsg.stores s, bsg.tr_hist t, bsg.member m
    -> WHERE p.pre_pev =143
    -> AND s.st_nbr = t.th_store
    -> AND t.th_mbpk = m.demog_id
    -> AND t.th_tdt
    -> BETWEEN '2007-01-01'
    -> AND '2007-01-31'
    -> AND m.bsg_uk = p.bsg_uk
    -> AND s.st_comdiv = 'BBSBBS';
+----+-------------+-------+------+-------------------------+---------+---------+------------------+--------+-------------+
| id | select_type | table | type | possible_keys           | key     | key_len | ref              | rows   | Extra       |
+----+-------------+-------+------+-------------------------+---------+---------+------------------+--------+-------------+
|  1 | SIMPLE      | p     | ref  | pre_pev                 | pre_pev |       2 | const            | 514170 | Using where |
|  1 | SIMPLE      | m     | ref  | PRIMARY,bsg_uk          | bsg_uk  |       4 | bsgtran.p.bsg_uk |      1 | Using where |
|  1 | SIMPLE      | t     | ref  | th_mbpk,th_tdt,th_store | th_mbpk |       4 | bsg.m.demog_id   |     12 | Using where |
|  1 | SIMPLE      | s     | ref  | st_nbr,st_comdiv        | st_nbr  |      15 | bsg.t.th_store   |      1 | Using where |
+----+-------------+-------+------+-------------------------+---------+---------+------------------+--------+-------------+
4 rows in set (0.01 sec)

mysql>