sufleR/sql_query

WITH RECURSIVE t AS (
  SELECT MIN(<%= @column_name %>) AS <%= @column_name %>
  FROM <%= @table_name %>
  UNION ALL
  SELECT (
    SELECT MIN(<%= @column_name %>) FROM <%= @table_name %>
    WHERE <%= @column_name %> > t.<%= @column_name %>)
  FROM t WHERE t.<%= @column_name %> IS NOT NULL
)
SELECT <%= @column_name %> FROM t WHERE <%= @column_name %> IS NOT NULL
<% if @with_nulls %>
  UNION ALL
  SELECT NULL WHERE EXISTS(SELECT 1 FROM <%= @table_name %> WHERE <%= @column_name %> IS NULL)
<% end %>