Once again, we see the actual SQL statement first: SELECT "lists".* FROM "lists". all method: 015:0> Album.allĪlbum Load (0.3ms) SELECT "albums".* FROM "albums" LIMIT $1 ] To see all of the records on the albums table, we can use the. In a production environment, any rollback is probably due to user error and the attempt to commit the record should fail silently, as it does with the standard #create and #save methods. We don't want our application to throw an exception if a record isn't saved to the database. These bang methods are great for debugging but should never be used in a production application. This time, the Song is successfully created. We specify that the value of album_id should be equal to album.id. We don't have to use the bang method, but it's useful here just in case we get another error. (As long as you've been following along with the lesson and haven't exited the console, it should.) Then we #create! the Song yet again. Song Create (32.3ms) INSERT INTO "songs" ("album_id", "created_at", "updated_at", "name") VALUES ($1, $2, $3, $4) RETURNING "id", ,, ]įirst, we verify that album exists. Let's try to create the record one more time: 013:0> albumĠ14:0> Song.create!(name: "Reckoner", album_id: album.id)Īlbum Load (0.2ms) SELECT "albums".* FROM "albums" WHERE "albums"."id" = $1 LIMIT $2, ] By default, the "many" must always have an association with the "one." In this case, that means that an instance of Song must have an album_id. However, Rails 5 has a built-in validation for one-to-many relationships.
#Rails command see all active tables how to#
We'll cover validations more in a future lesson, including how to create custom validations. Now we have a clear error message: Validation failed: Album must exist. Let's try again: 012:0> Song.create!(name: "Reckoner")ĪctiveRecord::RecordInvalid: Validation failed: Album must exist #create! and #save! cause our application to throw an exception if the record isn't committed to the database. We've learned that bang methods are usually destructive, but not in this case. Our new Song hasn't been saved to the database.įortunately, the #create method can also be a bang method like this: #create!.
Instead of getting a COMMIT message, we get a ROLLBACK message instead. If we want to return the new row from the database, we'll use #create instead. If we want the method to return a boolean, then we'll favor using the #save method. Notice that after the #create method, the new record is returned instead of a boolean value as we saw with #save. We can perform the new and save events in a single action with the #create method: Album.create(name: "Giant Steps")Īlbum Create (0.3ms) INSERT INTO "albums" ("name", "created_at", "updated_at") VALUES ($1, $2, $3) RETURNING "id", , ] Currently, those two timestamps are the same because we haven't updated the album. One shows when it was created and the other shows when it was last updated. Note that the album now has two timestamps. Now, we can look at our album object and see the other properties that have been set by the database when we saved. The database returns the value true to indicate that the save was successful. The #save method triggers a SQL INSERT that creates a new record on the albums table for our album object as seen between the BEGIN and COMMIT.
Now we can assign values to this Album: 2.2.0 :002 > album.name="In Rainbows"įinally, we can save it with album.save(): 2.2.0 :004 > album.saveĪlbum Create (0.4ms) INSERT INTO "albums" ("name", "created_at", "updated_at") VALUES ($1, $2, $3) RETURNING "id", , ] You'll see after the => that an empty instance of Album is returned with no values in any of its properties. New and Save 2.2.0 :001 > album = Album.new First, we'll use the #new and #save methods. We'll start by creating a few new Albums and Songs in the database. Creating Database Entries Through the Console We can also use a shorter command: $ rails cīecause our Album model inherits from the ActiveRecord::Base class, we can use Active Record CRUD methods to explore and manipulate data in the database. We can open the Rails console from the terminal like this: $ rails console In this lesson, we'll practice using the rails console and try out some of the methods that Active Record provides us. Instead, we should use the Rails console. Most Rails developers rarely use psql to look at the database data. We can use it to try out commands, query the database, and debug our application.
The Rails console is a powerful IRB shell loaded with the Rails development environment.
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