隐式路径关联

SELECT
  AUTHOR.ID, (
    SELECT COUNT(*) FROM BOOK
    WHERE BOOK.AUTHOR_ID = AUTHOR.ID
  )
FROM AUTHOR

// Count the number of books per author
create.select(
          AUTHOR.ID,
          field(selectCount().from(AUTHOR.book())))
      .from(AUTHOR)
      .fetch();

// Get all books by author
create.select(
          AUTHOR.ID,
          multiset(selectFrom(AUTHOR.book())))
      .from(AUTHOR)
      .fetch();