Same query, 3 databases, 3 different results

The SQL standard leaves a lot of room for different implementations. This is a little demonstration of one of such differences.

SQLite  3.7.4

sqlite> create table t1 (id serial, t time);
sqlite> insert into t1(t) values ('00:05:10');
sqlite> select t,t*1.5 from t1;
00:05:10|0.0

MySQL 5.6.4-m5
mysql> create table t1 (id serial, t time);
Query OK, 0 rows affected (0.01 sec)

mysql> insert into t1(t) values ('00:05:10');
Query OK, 1 row affected (0.00 sec)

mysql> select t,t*1.5 from t1;
+----------+-------+
| t        | t*1.5 |
+----------+-------+
| 00:05:10 |   765 |
+----------+-------+
1 row in set (0.00 sec)

PostgreSQL 9.0.3
test=# create table t1 (id serial, t time);
NOTICE:  CREATE TABLE will create implicit sequence "t1_id_seq" for serial column "t1.id"
CREATE TABLE
test=# insert into t1(t) values ('00:05:10');
INSERT 0 1
test=# select t,t*1.5 from t1;
    t     | ?column?
----------+----------
 00:05:10 | 00:07:45
(1 row)

I think that the behaviour from PostgreSQL is the correct one. MySQL will just remove the :'s to get the string 000510 and then multiplies that value. The behaviour from SQLite is even more strange.

Of course for MySQL you could use the time_to_sec and sec_to_time functions.

mysql> select t,sec_to_time(time_to_sec(t)*1.5) from t1;
+----------+-------------------------------+
| t        | sec_to_time(time_to_sec(t)*2) |
+----------+-------------------------------+
| 00:05:10 | 00:07:45                      |
+----------+-------------------------------+
1 row in set (0.00 sec)

But those functions are not available on SQLite.

sqlite> select t,sec_to_time(time_to_sec(t)*1.5) from t1;
Error: no such function: sec_to_time