Lesson 7.4: Value comparisons

TypeQL provides several operators for comparing the values of attributes and literals in patterns.

Equality operators: ==, !=
Ordering operators: >, >=, <, <=
String matching operators: contains, like Concept equality: is

We have already seen a few examples of them in previous lessons.

Equality operators

The equality operators are valid for comparing values of all value types. We can compare the values of attributes either to those of literals or to those of each other. In the following Fetch query, we retrieve a list of books that were published in a city other than New York.

match
$book isa book;
($book, $publication) isa publishing;
($publication, $city) isa locating;
$city isa city, has name != "New York City";
fetch {
  "isbn": $book.isbn-13,
};

In this next query, we retrieve pairs of books that were published in the same year.

match
$book-1 isa book;
$book-2 isa book;
publishing ($book-1, $publication-1);
publishing ($book-2, $publication-2);
$publication-1 isa publication, has year $year-1;
$publication-2 isa publication, has year $year-2;
not { $book-1 is $book-2; };
$year-1 == $year-2;
fetch {
  "isbn-1": $book-1.isbn-13,
  "isbn-2": $book-2.isbn-13,
};

Ordering operators

The ordering operators can be used to compare any value type. We have already seen an example of their use in Lesson 7.3, where we retrieved a list of books that a user has eiter ordered or reviewed with a score of seven or higher.

match
$user isa user, has id "u0008";
$liked-book isa book;
{
    action-execution ($user, $order);
    order-line ($order, $liked-book);
} or {
    action-execution ($user, $review);
    rating ($review, $liked-book);
    $review has score >= 7;
};
fetch {
  "isbn": $liked-book.isbn-13,
};

In this next query we retrieve a list of books that have a retail price under $15.

match
$book isa book, has price <= 15.00;
fetch {
  "isbn": $book.isbn-13,
  "title": $book.title,
  "price": $book.price,
};

Exercise

Write a Fetch query to retrieve the IDs of orders that were placed during the Holiday Sale 2023. The entity representing this sale has the code "HOL23".

You may find it useful to refer to the bookstore’s schema.

Schema

define

entity book @abstract,
    owns isbn @card(0..2),
    owns isbn-13 @key,
    owns isbn-10 @unique,
    owns title,
    owns page-count,
    owns genre @card(0..),
    owns price,
    plays contribution:work,
    plays publishing:published,
    plays promotion-inclusion:item,
    plays order-line:item,
    plays rating:rated,
    plays recommendation:recommended;

entity hardback sub book,
    owns stock;

entity paperback sub book,
    owns stock;

entity ebook sub book;

entity contributor,
    owns name,
    plays contribution:contributor,
    plays authoring:author,
    plays editing:editor,
    plays illustrating:illustrator;

entity company @abstract,
    owns name;

entity publisher sub company,
    plays publishing:publisher;

entity courier sub company,
    plays delivery:deliverer;

entity publication,
    owns year,
    plays publishing:publication,
    plays locating:located;

entity user,
    owns id @key,
    owns name,
    owns birth-date,
    plays action-execution:executor,
    plays locating:located,
    plays recommendation:recipient;

entity order,
    owns id @key,
    owns status,
    plays order-line:order,
    plays action-execution:action,
    plays delivery:delivered;

entity promotion,
    owns code @key,
    owns name,
    owns start-timestamp,
    owns end-timestamp,
    plays promotion-inclusion:promotion;

entity review,
    owns id @key,
    owns score,
    owns verified,
    plays rating:review,
    plays action-execution:action;

entity login,
    owns success,
    plays action-execution:action;

entity address,
    owns street,
    plays delivery:destination,
    plays locating:located;

entity place @abstract,
    owns name,
    plays locating:located,
    plays locating:location;

entity city sub place;

entity state sub place;

entity country sub place;

relation contribution,
    relates contributor,
    relates work;

relation authoring sub contribution,
    relates author as contributor;

relation editing sub contribution,
    relates editor as contributor;

relation illustrating sub contribution,
    relates illustrator as contributor;

relation publishing,
    relates publisher,
    relates published,
    relates publication;

relation promotion-inclusion,
    relates promotion,
    relates item,
    owns discount;

relation order-line,
    relates order,
    relates item,
    owns quantity,
    owns price;

relation rating,
    relates review,
    relates rated;

relation action-execution,
    relates action,
    relates executor,
    owns timestamp;

relation delivery,
    relates deliverer,
    relates delivered,
    relates destination;

relation locating,
    relates located,
    relates location;

relation recommendation,
    relates recommended,
    relates recipient;

attribute isbn @abstract, value string;
attribute isbn-13 sub isbn;
attribute isbn-10 sub isbn;
attribute title, value string;
attribute page-count, value integer;
attribute genre, value string;
attribute stock, value integer;
attribute price, value double;
attribute discount, value double;
attribute id, value string;
attribute code, value string;
attribute name, value string;
attribute birth-date, value datetime;
attribute street, value string;
attribute year, value integer;
attribute quantity, value integer;
attribute score, value integer;
attribute verified, value boolean;
attribute timestamp, value datetime;
attribute start-timestamp, value datetime;
attribute end-timestamp, value datetime;
attribute status, value string @regex("^(paid|dispatched|delivered|returned|canceled)$");
attribute success, value boolean;

# TODO: Change to check
fun is_review_verified_by_purchase($review: review) -> { order }:
  match
    ($review, $product) isa rating;
    ($order, $product) isa order-line;
    ($user, $review) isa action-execution, has timestamp $review-time;
    ($user, $order) isa action-execution, has timestamp $order-time;
    $review-time > $order-time;
  return { $order };

fun book_recommendations_for($user: user) -> {book}:
  match
    $new-book isa book;
    {
        let $new-book in book_recommendations_by_author($user);
    } or {
        let $new-book in book_recommendations_by_genre($user);
    };
  return { $new-book };

fun book_recommendations_by_genre($user: user) -> { book }:
match
    $user isa user;
    $liked-book isa book;
    {
        ($user, $order-for-liked) isa action-execution;
        ($order-for-liked, $liked-book) isa order-line;
    } or {
        ($user, $review-for-liked) isa action-execution;
        ($review-for-liked, $liked-book) isa rating;
        $review-for-liked has score >= 7;
    };
    $new-book isa book;
    not { {
        ($user, $order-for-new) isa action-execution;
        ($order-for-new, $new-book) isa order-line;
    } or {
        ($user, $review-for-new) isa action-execution;
        ($review-for-new, $new-book) isa rating;
    }; };
    $liked-book has genre $shared-genre;
    $new-book has genre $shared-genre;
    not { {
        $shared-genre == "fiction";
    } or {
        $shared-genre == "nonfiction";
    }; };
  return { $new-book };

fun book_recommendations_by_author($user: user) -> { book }:
  match
    $user isa user;
    $liked-book isa book;
    {
        ($user, $order-for-liked) isa action-execution;
        ($order-for-liked, $liked-book) isa order-line;
    } or {
        ($user, $review-for-liked) isa action-execution;
        ($review-for-liked, $liked-book) isa rating;
        $review-for-liked has score >= 7;
    };
    $new-book isa book;
    not { {
        ($user, $order-for-new) isa action-execution;
        ($order-for-new, $new-book) isa order-line;
    } or {
        ($user, $review-for-new) isa action-execution;
        ($review-for-new, $new-book) isa rating;
    }; };
    ($liked-book, $shared-author) isa authoring;
    ($new-book, $shared-author) isa authoring;
  return { $new-book };

fun order_line_best_price($line: order-line) -> { double }:
  match
    ($order) isa action-execution, has timestamp $order-time;
    $line isa order-line, links ($order, $item);
    $item has price $retail-price;
    let $time_value = $order-time;
    let $best-discount = best_discount_for_item($item, $time_value);
    let $discounted-price = round(100 * $retail-price * (1 - $best-discount)) / 100;
    $line has quantity $quantity;
    let $line-total = $quantity * $discounted-price;
  return { $line-total };

fun best_discount_for_item($item: book, $order-time: datetime) -> double:
  match
    {
        $inclusion isa promotion-inclusion,
            links ($promotion, $item),
            has discount $discount-attr;
        $promotion has start-timestamp <= $order-time,
            has end-timestamp >= $order-time;
        let $discount = $discount-attr;
    } or {
        let $discount = 0.0; # default
    };
return max($discount);

fun transitive_places($place: place) -> { place }:
  match
    {
      locating (located: $place, location: $parent);
    } or {
      locating (located: $place, location: $middle);
      let $parent in transitive_places($middle);
    };
  return { $parent };

Sample solution

match
$holiday-order isa order;
action-execution ($holiday-order),
    has timestamp $order-time;
$holiday-sale isa promotion,
    has code "HOL23",
    has start-timestamp <= $order-time,
    has end-timestamp >= $order-time;
fetch {
  "order-id": $holiday-order.id,
};

The ordering operators are also valid for strings, use lexicographic ordering.

String matching operators

TypeQL includes two operators for string matching, denoted by the keywords contains and like. The contains operator checks if one string contains another in a case-insensitive manner, while the like operator can be used to match strings through Regex. Unlike the equality and ordering operators, the string matching operators can only be used to compare attribute values to string literals; they cannot be used to compare the values of two attributes.

The following query uses the contains operator to retrieve a list of books with both "electron" and "diffraction" in the title.

match
$book isa book, has title $title;
$title contains "electron";
$title contains "diffraction";
fetch {
  "title": $book.title,
};

{
  "title": "Electron Backscatter Diffraction in Materials Science"
}
{
  "title": "Interpretation of Electron Diffraction Patterns"
}

For non-Latin characters, the case insensitivity of the contains operator can result in unexpected behaviour.

Meanwhile, the following query uses the like operator to retrieve a list of books whose titles start with "the".

match
$book isa book, has title like "(?i)^the\s.*";
fetch {
  "title": $book.title,
};

Note: in Console, you might have to escape the \ as `\\`

{
  "title": "The Complete Calvin and Hobbes"
}
{
  "title": "The Hitchhiker's Guide to the Galaxy"
}
{
  "title": "The Hobbit"
}
{
  "title": "The Iron Giant"
}
{
  "title": "The Motorcycle Diaries: A Journey Around South America"
}
{
  "title": "The Mummies of Urumchi"
}
{
  "title": "The Odyssey"
}

Exercise

Write a Fetch query to retrieve the titles of books that contain "the" in a position other than the start.

You may find it useful to refer to the bookstore’s schema.

Schema

define

entity book @abstract,
    owns isbn @card(0..2),
    owns isbn-13 @key,
    owns isbn-10 @unique,
    owns title,
    owns page-count,
    owns genre @card(0..),
    owns price,
    plays contribution:work,
    plays publishing:published,
    plays promotion-inclusion:item,
    plays order-line:item,
    plays rating:rated,
    plays recommendation:recommended;

entity hardback sub book,
    owns stock;

entity paperback sub book,
    owns stock;

entity ebook sub book;

entity contributor,
    owns name,
    plays contribution:contributor,
    plays authoring:author,
    plays editing:editor,
    plays illustrating:illustrator;

entity company @abstract,
    owns name;

entity publisher sub company,
    plays publishing:publisher;

entity courier sub company,
    plays delivery:deliverer;

entity publication,
    owns year,
    plays publishing:publication,
    plays locating:located;

entity user,
    owns id @key,
    owns name,
    owns birth-date,
    plays action-execution:executor,
    plays locating:located,
    plays recommendation:recipient;

entity order,
    owns id @key,
    owns status,
    plays order-line:order,
    plays action-execution:action,
    plays delivery:delivered;

entity promotion,
    owns code @key,
    owns name,
    owns start-timestamp,
    owns end-timestamp,
    plays promotion-inclusion:promotion;

entity review,
    owns id @key,
    owns score,
    owns verified,
    plays rating:review,
    plays action-execution:action;

entity login,
    owns success,
    plays action-execution:action;

entity address,
    owns street,
    plays delivery:destination,
    plays locating:located;

entity place @abstract,
    owns name,
    plays locating:located,
    plays locating:location;

entity city sub place;

entity state sub place;

entity country sub place;

relation contribution,
    relates contributor,
    relates work;

relation authoring sub contribution,
    relates author as contributor;

relation editing sub contribution,
    relates editor as contributor;

relation illustrating sub contribution,
    relates illustrator as contributor;

relation publishing,
    relates publisher,
    relates published,
    relates publication;

relation promotion-inclusion,
    relates promotion,
    relates item,
    owns discount;

relation order-line,
    relates order,
    relates item,
    owns quantity,
    owns price;

relation rating,
    relates review,
    relates rated;

relation action-execution,
    relates action,
    relates executor,
    owns timestamp;

relation delivery,
    relates deliverer,
    relates delivered,
    relates destination;

relation locating,
    relates located,
    relates location;

relation recommendation,
    relates recommended,
    relates recipient;

attribute isbn @abstract, value string;
attribute isbn-13 sub isbn;
attribute isbn-10 sub isbn;
attribute title, value string;
attribute page-count, value integer;
attribute genre, value string;
attribute stock, value integer;
attribute price, value double;
attribute discount, value double;
attribute id, value string;
attribute code, value string;
attribute name, value string;
attribute birth-date, value datetime;
attribute street, value string;
attribute year, value integer;
attribute quantity, value integer;
attribute score, value integer;
attribute verified, value boolean;
attribute timestamp, value datetime;
attribute start-timestamp, value datetime;
attribute end-timestamp, value datetime;
attribute status, value string @regex("^(paid|dispatched|delivered|returned|canceled)$");
attribute success, value boolean;

# TODO: Change to check
fun is_review_verified_by_purchase($review: review) -> { order }:
  match
    ($review, $product) isa rating;
    ($order, $product) isa order-line;
    ($user, $review) isa action-execution, has timestamp $review-time;
    ($user, $order) isa action-execution, has timestamp $order-time;
    $review-time > $order-time;
  return { $order };

fun book_recommendations_for($user: user) -> {book}:
  match
    $new-book isa book;
    {
        let $new-book in book_recommendations_by_author($user);
    } or {
        let $new-book in book_recommendations_by_genre($user);
    };
  return { $new-book };

fun book_recommendations_by_genre($user: user) -> { book }:
match
    $user isa user;
    $liked-book isa book;
    {
        ($user, $order-for-liked) isa action-execution;
        ($order-for-liked, $liked-book) isa order-line;
    } or {
        ($user, $review-for-liked) isa action-execution;
        ($review-for-liked, $liked-book) isa rating;
        $review-for-liked has score >= 7;
    };
    $new-book isa book;
    not { {
        ($user, $order-for-new) isa action-execution;
        ($order-for-new, $new-book) isa order-line;
    } or {
        ($user, $review-for-new) isa action-execution;
        ($review-for-new, $new-book) isa rating;
    }; };
    $liked-book has genre $shared-genre;
    $new-book has genre $shared-genre;
    not { {
        $shared-genre == "fiction";
    } or {
        $shared-genre == "nonfiction";
    }; };
  return { $new-book };

fun book_recommendations_by_author($user: user) -> { book }:
  match
    $user isa user;
    $liked-book isa book;
    {
        ($user, $order-for-liked) isa action-execution;
        ($order-for-liked, $liked-book) isa order-line;
    } or {
        ($user, $review-for-liked) isa action-execution;
        ($review-for-liked, $liked-book) isa rating;
        $review-for-liked has score >= 7;
    };
    $new-book isa book;
    not { {
        ($user, $order-for-new) isa action-execution;
        ($order-for-new, $new-book) isa order-line;
    } or {
        ($user, $review-for-new) isa action-execution;
        ($review-for-new, $new-book) isa rating;
    }; };
    ($liked-book, $shared-author) isa authoring;
    ($new-book, $shared-author) isa authoring;
  return { $new-book };

fun order_line_best_price($line: order-line) -> { double }:
  match
    ($order) isa action-execution, has timestamp $order-time;
    $line isa order-line, links ($order, $item);
    $item has price $retail-price;
    let $time_value = $order-time;
    let $best-discount = best_discount_for_item($item, $time_value);
    let $discounted-price = round(100 * $retail-price * (1 - $best-discount)) / 100;
    $line has quantity $quantity;
    let $line-total = $quantity * $discounted-price;
  return { $line-total };

fun best_discount_for_item($item: book, $order-time: datetime) -> double:
  match
    {
        $inclusion isa promotion-inclusion,
            links ($promotion, $item),
            has discount $discount-attr;
        $promotion has start-timestamp <= $order-time,
            has end-timestamp >= $order-time;
        let $discount = $discount-attr;
    } or {
        let $discount = 0.0; # default
    };
return max($discount);

fun transitive_places($place: place) -> { place }:
  match
    {
      locating (located: $place, location: $parent);
    } or {
      locating (located: $place, location: $middle);
      let $parent in transitive_places($middle);
    };
  return { $parent };

Sample solution

match
$book isa book, has title like "(?i).+\sthe\s.*";
fetch {
  "title": $book.title,
};

Write a Fetch query to retrieve the ISBN-13s of all books that are included in an order that has a status of "paid", "dispatched", or "delivered", without using a disjunction (note: this is less performant than using a disjunction!)

Sample solution

match
$book isa book;
$order isa order;
order-line ($book, $order);
$order has status like "^(paid|dispatched|delivered)$";
fetch {
  "isbn": $book.isbn-13,
};

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Content

Lesson 7.4: Value comparisons

Equality operators

Ordering operators

String matching operators