# How to link two tables on a Rail page? **URL:** \ **Category:** Rails\ **Created:** [December 11, 2005, 12:54am UTC](https://www.ruby-forum.com/t/how-to-link-two-tables-on-a-rail-page/49957 "2005-12-11T00:54:11Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Cedric\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/65b543/32.png) [@Cedric\_G](https://www.ruby-forum.com/u/Cedric_G)\ **Post date:** [December 11, 2005, 12:54am UTC](https://www.ruby-forum.com/t/how-to-link-two-tables-on-a-rail-page/49957/1 "2005-12-11T00:54:11Z")
I have 2 MYSQL tables correctly linked to my Rail application. Table#1 represents the class Users Table#2 represents the class Timezone I can display the fields I want on Rails pages such as user/view or timezone/view (when only accessing one table in a page). However I am not able to view a page that would include a few columns of BOTH the user table + one column from the timezone table. Both tables are linked by the id field. I believe the model is properly defined in \model by using a “belong to” and “has many” statements to link both table. - I try to display the timezone column by using user.timezone.time\_zone\_name but I systematically get the following error message (winXP, rail .14, msql 5, webrick): " You have a nil object when you didn’t expect it! The error occured while evaluating nil.time\_zone\_name" Any idea what is the problem? Thanks, Cedric G. ---
**Author:** ![Cedric\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/65b543/32.png) [@Cedric\_G](https://www.ruby-forum.com/u/Cedric_G)\ **Post date:** [December 11, 2005, 1:47am UTC](https://www.ruby-forum.com/t/how-to-link-two-tables-on-a-rail-page/49957/2 "2005-12-11T01:47:11Z")
Hi Cedric, Apparently the user you are referencing does not have a timezone. In the timezone table is there a timezone entry whose user\_id is the same as the ID of the user you are referencing in the view? -Frank ---
**Author:** ![Cedric\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/65b543/32.png) [@Cedric\_G](https://www.ruby-forum.com/u/Cedric_G)\ **Post date:** [December 11, 2005, 1:51am UTC](https://www.ruby-forum.com/t/how-to-link-two-tables-on-a-rail-page/49957/3 "2005-12-11T01:51:15Z")
On 12/10/05, Cedric G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > BOTH the user table + one column from the timezone table. Both tables > The error occured while evaluating nil.time\_zone\_name" > > Any idea what is the problem? user.timezone is nil. ---
**Author:** ![Cedric\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/65b543/32.png) [@Cedric\_G](https://www.ruby-forum.com/u/Cedric_G)\ **Post date:** [December 11, 2005, 2:12am UTC](https://www.ruby-forum.com/t/how-to-link-two-tables-on-a-rail-page/49957/4 "2005-12-11T02:12:17Z")
railsonly wrote: > Hi Cedric, > Apparently the user you are referencing does not have a timezone. In > the > timezone table is there a timezone entry whose user\_id is the same as > the ID > of the user you are referencing in the view? > -Frank In my timezone table I have: - 2 columns: {id} and {time\_zone\_name} - 3 rows: {1} {Pacific}, {2} {Mountain}, {3} {Central}. In my user table I have - a few columns that include {id}, {user\_id}, …, (user\_time\_zone\_id} - so the rows are: {1} {1} {username1} … {2}, {2} {2} {username2} … {3} and {3} {3} {username3} … {1}. It is the user\_time\_zone\_id that establishes the link between the two tables so that instead of displaying “3” in the timezone for user2 I should have “Central” displayed. Suprisingly, I made typo and used user.timezone.id in the list.rhtml and I got another error message like this one: “Called id for nil, which would mistakenly be 4 – if you really wanted the id of nil, use object\_id” –\> it is very surprising to me that is “4” is mentionned. Because no id is = to 4. No idea where this is coming from. Thanks. Cedric ---
**Author:** ![Cedric\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/65b543/32.png) [@Cedric\_G](https://www.ruby-forum.com/u/Cedric_G)\ **Post date:** [December 11, 2005, 2:23am UTC](https://www.ruby-forum.com/t/how-to-link-two-tables-on-a-rail-page/49957/5 "2005-12-11T02:23:04Z")
When going thru the Rails doc I came accros this one: "… when you want to create a one-to-many foreign key relationship between, say, authors (note the plural!) and stories, you have to use a column author\_id in stories. The foreign key must be named in the format of: _singularOfForeignTableName_\_id. " I did not do that! I changed the field to timezone\_id in my user table and everything worked perfectly. Thanks for the help C- ---
**Author:** ![Cedric\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/65b543/32.png) [@Cedric\_G](https://www.ruby-forum.com/u/Cedric_G)\ **Post date:** [December 11, 2005, 2:27am UTC](https://www.ruby-forum.com/t/how-to-link-two-tables-on-a-rail-page/49957/6 "2005-12-11T02:27:54Z")
On 12/10/05, Cedric G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > - 2 columns: {id} and {time\_zone\_name} > > Suprisingly, I made typo and used user.timezone.id in the list.rhtml and > I got another error message like this one: “Called id for nil, which > would mistakenly be 4 – if you really wanted the id of nil, use > object\_id” > > → it is very surprising to me that is “4” is mentionned. Because no id > is = to 4. No idea where this is coming from. The id of ‘nil’ is 4. user.timezone is nil, and you’re asking for the id of nil. user.timezone needs to be set to a Timezone object. Or, you need to check to see if user.timezone is nil, and if it is, don’t try to display any information about it.