И правда. Сегодня пятница.
mysql> select '' = 0;
+--------+
| '' = 0 |
+--------+
| 1 |
+--------+
1 row in set (0,01 sec)
mysql> INSERT INTO `w` (`id_ecr`, `variety`, `lenght`, `color`, `img`, `id_f`) VALUES (1, '', '40', 'red', '', 1);
Query OK, 1 row affected (0,00 sec)
mysql> select * from w;
+--------+---------+--------+-------+-------+--------------+-----+------+
| id_ecr | variety | lenght | color | price | min_quantity | img | id_f |
+--------+---------+--------+-------+-------+--------------+-----+------+
| 1 | | 40 | red | 0.00 | 25 | | 1 |
+--------+---------+--------+-------+-------+--------------+-----+------+
1 row in set (0,00 sec)