count(column_name = nil, options = {})
Instance Public methods
Count the records.
Person.count # => the total count of all people Person.count(:age) # => returns the total count of all people whose age is present in database Person.count(:all) # => performs a COUNT(*) (:all is an alias for '*') Person.distinct.count(:age) # => counts the number of different age values
If count is used with group, it returns a Hash whose keys represent the aggregated column,
and the values are the respective amounts:
Person.group(:city).count
# => { 'Rome' => 5, 'Paris' => 3 }
If count is used with select, it will count the
selected columns:
Person.select(:age).count # => counts the number of different age values
Note: not all valid select expressions are valid
count expressions. The specifics differ between databases. In
invalid cases, an error from the databsae is thrown.
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