Check out example codes for "arel_table rails". It will help you in understanding the concepts better.
Code Example 1
Address.where( Address.arel_table[:created_at].lt( 5.days.ago ) ).to_sql
# SELECT "addresses".* FROM "addresses" WHERE ("addresses"."created_at" < '2016-12-13 03:31:23.911914')
Code Example 2
veg = Arel::Table.new(:vegetables)
query = veg[:created_at].gteq( 5.days.ago ).and(
veg[:color].eq("green").or(
veg[:gardener].eq("Susan")
)
)
query.to_sql
# "vegetables"."created_at" >= '2016-12-13 03:54:28.575342'
# AND ("vegetables"."color" = 'green' OR "vegetables"."gardener" = 'Susan')
Vegetable.where( query )
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