Rails: how can I get unique values from column

Question

How can I get unique values from column in the table? For example, I have this Products table:

ID NAME CATEGORY
1 name1 1st_cat
2 name2 2nd_cat
3 name3 1st_c         


        

Answer 1

For postgres

<% Product.select("DISTINCT ON (category) *").each do |category|
    <%= category %>
    <%= name %>
<% end %>

---

Update

even better

<% Product.select(%(DISTINCT ON (category) "#{Product.table_name}".*)).each do |category|
    <%= category %>
    <%= name %>
<% end %>

because it can return wrong columns when you do joins (e.g. returns id column from joined table, but not products)