Ruby-on-rails – Active Record – Get the second, third.. item in a database (without ID)

activerecorddatabaseruby-on-railsruby-on-rails-3

How to I retrieve the second, third .. entries in a database. I don't want to use the auto incrementing id generated by rails.

As I am deleting entries from my database, so the ID continues to increase.

So my DB would have

id : 210 (Even thought it's currently the first value)
id : 211 (Even thought it's currently the second value)

I know "Phone.first" will return the first how do I get the second.

Sub Question-
Destroy_all/delete_all –
only removes the item, Can I remove all entries from the DB and have the DB id's start from one without dropping the table. As I ran into problems.

Best Answer

Say you want the fourth user:

 @users = User.limit(4)
 @fourth_user = @users[3]

Concerning your second question, destroy_all should do the trick since it triggers all callbacks. Be sure to add :dependent => :destroy in your relationships.

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Sql – How to list the tables in a SQLite database file that was opened with ATTACH

There are a few steps to see the tables in an SQLite database:

List the tables in your database:
```
.tables
```
List how the table looks:
```
.schema tablename
```
Print the entire table:
```
SELECT * FROM tablename;
```
List all of the available SQLite prompt commands:
```
.help
```

Ruby-on-rails – validates_uniqueness_of passes on nil or blank (without allow_nil and allow_blank)

You are mistaken about the default behavior. From the docs:

:allow_nil - If set to true, skips this validation if the attribute is nil (default is false). :allow_blank - If set to true, skips this validation if the attribute is blank (default is false, it includes nil too).

Setting allow_blank to true, I see the following behavior with Rails 2.3.4.

class Thing < ActiveRecord::Base
  validates_uniqueness_of :identification, :allow_blank => true
end

>> Thing.create! :identification => ""
=> #<Thing id: 6, identification: "", created_at: "2009-09-26 03:09:48", updated_at: "2009-09-26 03:09:48">
>> Thing.create! :identification => ""
=> #<Thing id: 7, identification: "", created_at: "2009-09-26 03:09:49", updated_at: "2009-09-26 03:09:49">
>> Thing.create! :identification => nil
=> #<Thing id: 8, identification: nil, created_at: "2009-09-26 03:09:52", updated_at: "2009-09-26 03:09:52">
>> Thing.create! :identification => nil
=> #<Thing id: 9, identification: nil, created_at: "2009-09-26 03:09:53", updated_at: "2009-09-26 03:09:53">

Edit: Addressing your clarification.

Adding a validates_presence_of would be correct for what you're trying to do. It's not redundant, since it's checking for a completely different error case. It also has its own error message, which will be important for the user.

class Thing < ActiveRecord::Base
  validates_uniqueness_of :identification, :allow_blank => true
  validates_presence_of :identification
end

Best Answer

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Sql – How to list the tables in a SQLite database file that was opened with ATTACH

Ruby-on-rails – validates_uniqueness_of passes on nil or blank (without allow_nil and allow_blank)

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