Promedio de Tiempos en MYSQL

[leonardo_josue]

Y como complemento, te recuerdo que '00:00:00' es diferente de NULL (lo mismo que una cadena vacía ('')), mucho ojo con eso:

Código MySQL:

mysql> SELECT * FROM horas;
+----+----------+
| id | hora     |
+----+----------+
|  1 | 00:04:33 |
|  2 | NULL     |
|  3 | 00:00:00 |
+----+----------+
3 rows in set (0.00 sec)
 
mysql> SELECT * FROM horas WHERE hora IS NULL;
+----+------+
| id | hora |
+----+------+
|  2 | NULL |
+----+------+
1 row in set (0.00 sec)
 
mysql> SELECT * FROM horas WHERE hora IS NOT NULL;
+----+----------+
| id | hora     |
+----+----------+
|  1 | 00:04:33 |
|  3 | 00:00:00 |
+----+----------+
2 rows in set (0.00 sec)
 
mysql> SELECT * FROM horas WHERE hora = '00:00:00';
+----+----------+
| id | hora     |
+----+----------+
|  3 | 00:00:00 |
+----+----------+
1 row in set (0.00 sec)
 
mysql> SELECT * FROM horas WHERE hora != '00:00:00';
+----+----------+
| id | hora     |
+----+----------+
|  1 | 00:04:33 |
+----+----------+
1 row in set (0.00 sec)
 

Saludos
Leo.