Querying the database

All queries in ActiveAndroid use the query builder syntax, or the Model.query() method.

Let's look at some queries by adding to our model. Here's what we have so far:

@Table(name = "Items")
public class Item extends Model {
	@Column(name = "Name")
	public String name;

	@Column(name = "Category")
	public Category category;
}

It would be nice if we could get a random item from the database. Let's add a method to do that.

public static Item getRandom() {
	return new Select().from(Item.class).orderBy("RANDOM()").executeSingle();
}

Building a query in ActiveAndroid is like building a normal SQL statement. We create a new select object, call from and pass in the Item class. We then call orderBy, passing in "RANDOM". To execute a query we call execute(), or in this case executeSingle().

If we only want to get items from a certain category, we pass in a string for our where class argument. The method would look like this:

public static Item getRandom(Category category) {
	return new Select()
		.from(Item.class)
		.where("Category = ?", category.getId())
		.orderBy("RANDOM()")
		.executeSingle();
}

And here's how we get all the items in a category, sorted by name.

public static List<Item> getAll(Context context, Category category) {
	return new Select()
		.from(Item.class)
		.where("Category = ?", category.getId())
		.orderBy("Name ASC")
		.execute();
}

Next, let's explore Type serializers.