Example:
2.2.4 :006 > Product.create(name: ‘product1’, total: 10, price: 10.2)
(0.3ms) begin transaction
SQL (0.9ms) INSERT INTO "products" ("name", "total", "price") VALUES (?, ?, ?) [["name", "product1"], ["total", 10], ["price", 10.2]]
(0.6ms) commit transaction
=> #<Product id: 1, name: "product1", total: 10, price: #<BigDecimal:7fa0fb90cc18,'0.102E2',18(36)>>
2.2.4 :003 > Order.create(product: Product.first, total: 4)
Product Load (0.2ms) SELECT "products".* FROM "products" ORDER BY "products"."id" ASC LIMIT 1
(0.3ms) begin transaction
SQL (1.8ms) INSERT INTO "orders" ("product_id", "total") VALUES (?, ?) [["product_id", 1], ["total", 4]]
SQL (0.2ms) UPDATE "products" SET "total" = ? WHERE "products"."id" = ? [["total", 6], ["id", 1]]
(0.6ms) commit transaction
=> #<Order id: 1, product_id: 1, total: 4>
2.2.4 :004 > Product.first
Product Load (1.5ms) SELECT "products".* FROM "products" ORDER BY "products"."id" ASC LIMIT 1 => #<Product id: 1, name: "product1", total: 6, price: #<BigDecimal:7fa0fc17dbb8,'0.102E2',18(36)>>