The Big Programming Thread - Page 840

	public static <T, K> boolean arrayEquals(T[] a1, K[] a2) {
		int length = a1.length;
		if (length != a2.length) {
			return false;
		}
		for (int i = 0; i < length; i++) {
			if (!Objects.equals(a1[i], a2[i])) {
				return false;
			}
		}
		return true;
	}

@Entity
public class Product {
	@id
	private Long id;
	private String productName;
	@ManyToOne
	private Brand brand;}

@Entity
public class Brand {
	@id
	private Long id;
	private String brandName;
	@OneToMany(mappedBy="brand")
	private Set <Product> products = new HashSet();
}

System.out.println(em.createQuery(
"SELECT n.brandName
FROM product p join p.brand
WHERE p.id = 17").getSingleResult();

	public static String ListToString(Object obj) {
		List<?> list = (List<?>) obj;
		StringBuilder sb = new StringBuilder();
		for (Object element : list) {
			sb.append(element);
			sb.append(" ");
		}
		return sb.toString();
	}

var e = obj as IEnumberable<object>;
if (null != e)
    return string.Join(" ", e);
return e.ToString();

public static <T> string ToCustomString(this IEnumerable<T> enumerable) 
{
  return enumerable.Select(elem => elem.ToString()).Join();
}

@Entity
public class Product {
	@id
	private Long id;
	private String productName;
	@ManyToOne
	private Brand brand;}

@Entity
public class Brand {
	@id
	private Long id;
	private String brandName;
	@OneToMany(mappedBy="brand")
	private Set <Product> products = new HashSet();
}

System.out.println(em.createQuery(
"SELECT n.brandName
FROM product p join p.brand
WHERE p.id = 17").getSingleResult();

Query q = em.createQuery(
    "SELECT b.name FROM brands b WHERE b.product_id = :productId")
    .setParameter("productId", 17)
    .getSingleResult();

Brand.where(product: product).pluck(:name).first

On February 10 2017 05:27 Manit0u wrote:
First of all, if the tables and columns are not provided, you should change productName and brandName to simply name. You avoid information duplication, and you don't do weird-looking things like Product.getProductName().

Now, on to the query:

Query q = em.createQuery(
    "SELECT b.name FROM brand b WHERE b.product_id = :productId")
    .setParameter("productId", 17)
    .getSingleResult();

That would be the optimal query. But getSingleResult() throws exception on null (which is a perfectly viable db response, mind you). Also, JPQL blows hard, but many things do after you've been using cool stuff like Doctrine and now ActiveRecord for Rails:

Brand.find_by(product: product).pluck(:name)

So much less writing superfluous stuff. You just state your intent and it happens

System.out.println(myEntityManager.find(Product.class, 17).getBrand().getBrandName()

On February 10 2017 05:45 Artesimo wrote:

Show nested quote +

On February 10 2017 05:27 Manit0u wrote:
First of all, if the tables and columns are not provided, you should change productName and brandName to simply name. You avoid information duplication, and you don't do weird-looking things like Product.getProductName().

Now, on to the query:

Query q = em.createQuery(
    "SELECT b.name FROM brand b WHERE b.product_id = :productId")
    .setParameter("productId", 17)
    .getSingleResult();

That would be the optimal query. But getSingleResult() throws exception on null (which is a perfectly viable db response, mind you). Also, JPQL blows hard, but many things do after you've been using cool stuff like Doctrine and now ActiveRecord for Rails:

Brand.find_by(product: product).pluck(:name)

So much less writing superfluous stuff. You just state your intent and it happens

Thanks a lot. I am currently doing pracitce exams so I just copy pasted straight from the PDF, so everything but the Query was given and I can't really do much beyond that. Not very confident when it comes to data bases.
Your non JPQL-example is the equivalent of getting

System.out.println(myEntityManager.find(Product.class, 17).getBrand().getBrandName()

I assume? I can't really say much about JPQL vs other stuff since I only know JPQL and even that only in theory.


EDIT: Wait... where does b.product_id actually comes from in your example? Does the ID-row of a Table accesed by TABLENAME_ROWNAME when accesed this way?

Query q = em.createQuery(
    "SELECT b.name FROM brand b
     JOIN producs p
     WHERE p.id = :productId")
    .setParameter("productId", 17)
    .getSingleResult();

Query q = em.createQuery(
    "SELECT b.name FROM brand b
     JOIN producs p
     WHERE p.id = :productId")
    .setParameter("productId", 17)
    .getSingleResult();

Query q = em.createQuery(
    "SELECT b.name FROM brand b
     JOIN b.products p
     WHERE p.id = :productId")
    .setParameter("productId", 17)
    .getSingleResult();

Query q = em.createQuery(
    "SELECT c.firstName, c.LastName, a.id 
     FROM Customer c, Accounts a
     JOIN c.accounts
     WHERE a.balance<0")

$brown: #955436
$lightblue: #AAE0FA
$pink: #D93A96
$orange: #F7941D
$red: #ED1B24
$yellow: #FEF224
$green: #1FB25A
$darkblue: #0072BB

.block-(colorexample)
    background-color:$colorexample

block-brown

$brown: #955436
$lightblue: #AAE0FA
$pink: #D93A96
$orange: #F7941D
$red: #ED1B24
$yellow: #FEF224
$green: #1FB25A
$darkblue: #0072BB

.block-(colorexample)
    background-color:$colorexample

block-brown

@mixin block($color) {
  .block-#{$color} {
    background-color: $color;
  }
}