Active Record

Question 1

find_in_batches

Answer 1

Yields each batch of records that was found by the find options as an array.:batch_size - Specifies the size of the batch. Default to 1000.:start - Specifies the starting point for the batch processing.

Question 2

find_each

Answer 2

The find_each method uses find_in_batches with a batch size of 1000

Question 3

column_names

Answer 3

Returns an array of column names as strings.

Question 4

column_defaults

Answer 4

Returns a hash where the keys are column names and the values are default values when instantiating the AR object for this table.

Question 5

User.where(‘name != ?’, ‘Gabe’)

Answer 5

Qureries the database for all Users where the name not Gabe

Question 6

User.where(‘name = ? AND last_name != ?’,’Gabe’,’Smith’)

Answer 6

Queries the database for all Users where the name is Gabe and the last name is not Smith

Question 7

User.where(‘age < 45’)

Answer 7

Queries the database for all Users where the age is less than 45.

Question 8

Person.destroy_all(conditions: nil)

Answer 8

Destroys records of the Person model matching conditions, or all if no condition is passed. Each object’s callbacks are executed.

Question 9

Person.delete_all(conditions: nil)

Answer 9

Deletes the records matching conditions without instantiating the records first, and hence not calling the destroy method nor invoking callbacks.

Question 10

Person.pluck(:name)

Answer 10

Returns an Array of attribute values type-casted to match the plucked column names, if they can be deduced.