Method: Sequel::Dataset#get

Defined in:
lib/sequel/dataset/actions.rb

#get(column = (no_arg=true; nil), &block) ⇒ Object

Return the column value for the first matching record in the dataset. Raises an error if both an argument and block is given.

DB[:table].get(:id) # SELECT id FROM table LIMIT 1
# => 3

ds.get{sum(id)} # SELECT sum(id) AS v FROM table LIMIT 1
# => 6

You can pass an array of arguments to return multiple arguments, but you must make sure each element in the array has an alias that Sequel can determine:

DB[:table].get([:id, :name]) # SELECT id, name FROM table LIMIT 1
# => [3, 'foo']

DB[:table].get{[sum(id).as(sum), name]} # SELECT sum(id) AS sum, name FROM table LIMIT 1
# => [6, 'foo']

If called on a dataset with raw SQL, returns the first value in the dataset without changing the selection or setting a limit:

DB["SELECT id FROM table"].get # SELECT id FROM table
# =>  3



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# File 'lib/sequel/dataset/actions.rb', line 312

def get(column=(no_arg=true; nil), &block)
  ds = naked
  if block
    raise(Error, 'Must call Dataset#get with an argument or a block, not both') unless no_arg
    ds = ds.select(&block)
    column = ds.opts[:select]
    column = nil if column.is_a?(Array) && column.length < 2
  elsif no_arg && opts[:sql]
    return ds.single_value!
  else
    case column
    when Array
      ds = ds.select(*column)
    when LiteralString, Symbol, SQL::Identifier, SQL::QualifiedIdentifier, SQL::AliasedExpression
      if loader = cached_placeholder_literalizer(:_get_loader) do |pl|
          ds.single_value_ds.select(pl.arg)
        end

        return loader.get(column)
      end

      ds = ds.select(column)
    else
      if loader = cached_placeholder_literalizer(:_get_alias_loader) do |pl|
          ds.single_value_ds.select(Sequel.as(pl.arg, :v))
        end

        return loader.get(column)
      end

      ds = ds.select(Sequel.as(column, :v))
    end
  end

  if column.is_a?(Array)
   if r = ds.single_record
     r.values_at(*hash_key_symbols(column))
   end
  else
    ds.single_value
  end
end