For possible educational research purposes, I was playing around with a
query that would randomly select people from a database. The database I
experiment with has a group of fictitious persons with id numbers
(primary key) ranging sequentially from 2 to 378. When I ran these
queries below, I was expecting to select five random persons from the
database. The query partially worked. I was getting random subjects, but
everytime I ran the query, I got a different number of subjects,
stretching from 0 and up (sometimes as many as 8 or 9). I could see the
query generating fewer rows if I duplicated an id or made an off-by-one
error, but I don't see how it could generate more than five. Does anyone
see my error? (I've used two equivalent forms for the query below; both
did the same thing)
select id,first,middle,last from persons where id = ceil(rand()*377+1)
or id = ceil(rand()*377+1) or id = ceil(rand()*377+1) or id =
ceil(rand()*377+1) or id = ceil(rand()*377+1);
select id,first,middle,last from persons where id in (ceil(rand()*377
+1), ceil(rand()*377+1), ceil(rand()*377+1), ceil(rand()*377+1),
ceil(rand()*377+1));
+------+-------------+--------+----------+
| id | first | middle | last |
+------+-------------+--------+----------+
| 35 | Viridiana | W | McCarthy |
| 47 | Crystal | O | Cassady |
| 67 | Ricardo | L | Johnson |
| 183 | Christopher | E | Denver |
| 237 | Christopher | B | Brenner |
| 255 | Danielle | W | Nickels |
| 299 | Christine | D | Dexter |
| 300 | Rachel | J | Baker |
| 339 | Jenna | O | Murray |
+------+-------------+--------+----------+
9 rows in set (0.00 sec)
