MySQL error no. 150 when trying to create foreign key -

i have 2 tables. 1 'subcategory' id auto-incrementing primary key.

from second table, 'product_subcategory' want have field category use 'subcategory.id' foreign key.

when using

alter table product_subcategory add constraint fk_subcategory_product  foreign key (subcategory) references subcategory(id); 

i receive error no. 150.

having looked error found this question answer states these conditions can lead error no 150:

1. 2 tables must engine=innodb. (can others: engine=myisam works too) 2. 2 tables must have same charset. 3. pk column(s) in parent table , fk column(s) must same data type. 4. pk column(s) in parent table , fk column(s), if have define collation type, must have same collation type; 5. if there data in foreign key table, fk column value(s) must match values in parent table pk columns. 6. , child table cannot temporary table. 

so used show table status confirm tables suitable:

 | name        | engine | version | row_format | rows | avg_row_length | data_length | max_data_length | index_length | data_free | auto_increment | create_time         | update_time | check_time | collation         | checksum | create_options | comment |  | subcategory | innodb |      10 | compact    |    0 |              0 |       16384 |               0 |        16384 |   6291456 |           null | 2013-07-31 16:37:03 | null        | null       | latin1_swedish_ci |     null |                |         | 

&

     | name                | engine | version | row_format | rows | avg_row_length | data_length | max_data_length | index_length | data_free | auto_increment | create_time         | update_time | check_time | collation         | checksum | create_options | comment | 

  | product_subcategory | innodb |      10 | compact    |    0 |              0 |       16384 |               0 |            0 |   6291456 |           null | 2013-07-31 16:35:04 | null        | null       | latin1_swedish_ci |     null |                |         | 

the difference being index_length.

the respective pk & fk column data identical can see , both tables empty.

does have suggestions may causing error no 150? or can suggest other areas me problem solve this?

edit: exact error message is:

error 1005 (hy000): can't create table 'ntm.#sql-31c_365' (errno: 150)

ddl info:

> -- mysql dump 10.13  distrib 5.5.31, debian-linux-gnu (x86_64) -- -- host: localhost    database: ntm -- ------------------------------------------------------ -- server version   5.5.31-0ubuntu0.13.04.1  /*!40101 set @old_character_set_client=@@character_set_client */; /*!40101 set @old_character_set_results=@@character_set_results */; /*!40101 set @old_collation_connection=@@collation_connection */; /*!40101 set names utf8 */; /*!40103 set @old_time_zone=@@time_zone */; /*!40103 set time_zone='+00:00' */; /*!40014 set @old_unique_checks=@@unique_checks, unique_checks=0 */; /*!40014 set @old_foreign_key_checks=@@foreign_key_checks, foreign_key_checks=0 */; /*!40101 set @old_sql_mode=@@sql_mode, sql_mode='no_auto_value_on_zero' */; /*!40111 set @old_sql_notes=@@sql_notes, sql_notes=0 */;  -- -- table structure table `product` --  drop table if exists `product`; /*!40101 set @saved_cs_client     = @@character_set_client */; /*!40101 set character_set_client = utf8 */; create table `product` (   `id` int(11) not null auto_increment,   `category` int(11) default null,   `name` varchar(255) default null,   `price` int(11) default null,   `tax` double default null,   `weight` int(11) default null,   `size` varchar(255) default null,   `discount` varchar(255) default null,   primary key (`id`),   key `fk_product_category` (`category`),   constraint `fk_product_category` foreign key (`category`) references `category` (`id`) ) engine=innodb default charset=latin1; /*!40101 set character_set_client = @saved_cs_client */;  -- -- table structure table `product_subcategory` --  drop table if exists `product_subcategory`; /*!40101 set @saved_cs_client     = @@character_set_client */; /*!40101 set character_set_client = utf8 */; create table `product_subcategory` (   `product` int(11) not null,   `subcategory` int(11) default null,   primary key (`product`),   constraint `fk_product_subcategory` foreign key (`product`) references `product` (`id`) ) engine=innodb default charset=latin1; /*!40101 set character_set_client = @saved_cs_client */;  -- -- table structure table `subcategory` --  drop table if exists `subcategory`; /*!40101 set @saved_cs_client     = @@character_set_client */; /*!40101 set character_set_client = utf8 */; create table `subcategory` (   `id` int(11) not null default '0',   `parent` int(11) default null,   `name` varchar(255) default null,   `text` longtext,   `summary` longtext,   `image` varchar(255) default null,   `featured` tinyint(1) default null,   primary key (`id`),   key `fk_sc_parent_id` (`parent`),   constraint `fk_sc_parent_id` foreign key (`parent`) references `category` (`id`) ) engine=innodb default charset=latin1; /*!40101 set character_set_client = @saved_cs_client */; /*!40103 set time_zone=@old_time_zone */;  /*!40101 set sql_mode=@old_sql_mode */; /*!40014 set foreign_key_checks=@old_foreign_key_checks */; /*!40014 set unique_checks=@old_unique_checks */; /*!40101 set character_set_client=@old_character_set_client */; /*!40101 set character_set_results=@old_character_set_results */; /*!40101 set collation_connection=@old_collation_connection */; /*!40111 set sql_notes=@old_sql_notes */; 

i tried , found mistyped capitalization in name of subcategory. table names in mysql case-sensitive when use os has case-sensitive filenames.

mysql> select version(); +---------------+ | version()     | +---------------+ | 5.6.12-56-log | +---------------+  mysql> alter table product_subcategory add constraint fk_subcategory_product  foreign key (subcategory) references subcategory(id); error 1215 (hy000): cannot add foreign key constraint  mysql> alter table product_subcategory add constraint fk_subcategory_product  foreign key (subcategory) references subcategory(id); query ok, 0 rows affected (0.33 sec) 

see http://dev.mysql.com/doc/refman/5.6/en/identifier-case-sensitivity.html more details.