In the last episode (Sep 18), Victor Subervi said: > Can someone please explain to me why Passengers.weight comes up null for > the last value sometimes, and other times it comes up with the value 155??
Passengers id 1 through 3 have a weight of NULL in the Passengers table, and passenger 4 has a weight of 155. Your first query ends up returning rows for only matches passengers 1 through 3, so you will always get NULL in the weight column. What were you expecting to see? > mysql> select p.id, c.id, p.name, p.weight, m.amount, p.round_trip, > c.first_name, c.middle_name, c.last_name, c.suffix, c.sex, p.confirmation, > m.type, m.payment, p.late_fee, p.late_fee_paid, m.discount from Passengers p > join Customers c join Money m on m.foreign_id=p.id and > m.customer_id=c.idwhere m.type="flight fee" and p.flight_id=1; > +----+----+------+--------+--------+------------+------------+-------------+-----------+--------+------+--------------+------------+---------+----------+---------------+----------+ > | id | id | name | weight | amount | round_trip | first_name | middle_name | > last_name | suffix | sex | confirmation | type | payment | late_fee | > late_fee_paid | discount | > +----+----+------+--------+--------+------------+------------+-------------+-----------+--------+------+--------------+------------+---------+----------+---------------+----------+ > | 1 | 1 | NULL | NULL | 70.00 | 0 | Adolph | NULL | > Hitler | NULL | Male | 123456 | flight fee | CC | no | > n/a | 0 | > | 2 | 1 | NULL | NULL | 70.00 | 0 | Adolph | NULL | > Hitler | NULL | Male | 987987987 | flight fee | cash | no | > n/a | 0 | > | 3 | 3 | NULL | NULL | 70.00 | 0 | Me | NULL | > Too | NULL | Male | 123456 | flight fee | CC | no | > n/a | 20 | > +----+----+------+--------+--------+------------+------------+-------------+-----------+--------+------+--------------+------------+---------+----------+---------------+----------+ > 3 rows in set (0.00 sec) > > mysql> select * from Passengers; > +----+-----------+-------------+------+------+--------+-------+------------+--------------+----------+---------------+ > | id | flight_id | customer_id | name | sex | weight | price | round_trip | > confirmation | late_fee | late_fee_paid | > +----+-----------+-------------+------+------+--------+-------+------------+--------------+----------+---------------+ > | 1 | 1 | 1 | NULL | Male | NULL | 0.00 | 0 | > 123456 | no | n/a | > | 2 | 1 | 1 | NULL | Male | NULL | 0.00 | 0 | > 987987987 | no | n/a | > | 3 | 1 | 2 | NULL | Male | NULL | 0.00 | 0 | > 123456 | no | n/a | > | 4 | 1 | 3 | NULL | Male | 155 | 70.00 | 0 | > 123456 | no | n/a | > +----+-----------+-------------+------+------+--------+-------+------------+--------------+----------+---------------+ > 4 rows in set (0.00 sec) > > mysql> select p.weight from Passengers p; > +--------+ > | weight | > +--------+ > | NULL | > | NULL | > | NULL | > | 155 | > +--------+ > 4 rows in set (0.00 sec) > > TIA, > Victor -- Dan Nelson dnel...@allantgroup.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org