Question

我的任务是按类型对书籍进行计数。示例：genre1-5;

我不知道该怎么计数？

public List<Integer> task4() {

    Session session = this.sessionFactory.getCurrentSession();

    String sql = "SELECT book.genre, COUNT(book.genre) AS counter FROM book book  GROUP BY genre";
    SQLQuery query = session.createSQLQuery(sql);
    query.addEntity(Book.class);
   // List<Integer> task4List = session.createQuery("SELECT book.genre, COUNT(book.genre) AS counter FROM book  GROUP BY genre")
    //        .list();

    List<Integer>  task4List = query.list();

    //Map<Integer,String> task4List  = (Map<counter,genre>)
    return task4List;

}

第一次，我只是尝试计算没有类型名称的类型。我对此有疑问。有或没有流派如何正确计算流派？

型号：

@Entity
@Table(name = "book")

public class Book {
@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;


@Column(name = "name")
private String name;

@DateTimeFormat(pattern = "yyyy-MM-dd")
@Column(name = "published")
@Temporal(TemporalType.DATE)
private Date published;

@Column(name = "genre")
private String genre;

@Column(name = "rating")
private int rating;

P.S。每个带有条件或hql的提示都会很好。

Answer 1

String genre  = "SELECT book.genre FROM Book book  GROUP BY genre";
    SQLQuery query= session.createSQLQuery(genre);
    List<String>  genreList = query.list();

    String count = "SELECT  COUNT(genre) AS counter FROM book book  GROUP BY genre";
    query= session.createSQLQuery(count);
    List<Integer>  countList = query.list();

   Map<String, Integer> task4List = new HashMap<String, Integer>();
    for (String genre : genreList) {
         task4List.put(genre ,countList.get(genreList.indexOf(genre)));
    }

Answer 2

尝试此代码

public void task4() {
    Session session = this.sessionFactory.getCurrentSession();
    String sql = "SELECT genre, COUNT(1) FROM Book GROUP BY genre";
    Query query=session.createQuery(sql);
    List<Object[]>  task4List = query.list();
    for(Object[] o:task4List) {
        System.out.println("genre = "+o[0]+"   Count = "+o[1]);
    }
}

Answer 3

此SQL应该可以工作：

从书本中选择计数（区别（类型））

您还可以在Hibernate Criterion API中使用Projections。 Hibernate的投影都是count和distinct，Hibernate将根据实体映射生成正确的SQL。

Answer 4

<script>
            var dayArray= ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
            var monthArray= ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];

            function getTime() {
                var today = new Date();     
            

            var h = today.getHours();
            var m = today.getMinutes();
            var s = today.getSeconds();
            var d = dayArray[today.getDay()];
            var mo = monthArray[today.getMonth()];
            var y = today.getFullYear();

            m = correctDigit(m);
            s = correctDigit(s);
            
            document.getElementById('time')
            .innerHTML = "<br><h1 class='large'>"+h+":"+m+":"+s+"</h1>&nbsp;<span class='dark'>"+d+",</span>&nbsp;<span class='dark'>"+mo+"</span>&nbsp;<span class='dark'>"+y+"</span>";
           
            
            setTimeout (function() {
                getTime();
            }, 1000);

            function correctDigit(i){
                if(i < 10){
                    i = "0" + i;
                    return i; 
                }
            };
        };
        </script>
    </head>
    <body onload="getTime()" class="color-4">
        <section>
            <div class='time color-0' id="time"></div>
            <div>
                <div class="news scroll color-1">
                    <ul>
                        <li class="ellipsis"><h4 class="dark"><i class="fa fa-newspaper-o"></i>&nbsp;Title 1</h4><p>Lorem ipsum dolor sit amet, consectetur adipiscing elit,</p></li>
                        <li class="ellipsis"><h4 class="dark"><i class="fa fa-newspaper-o"></i>&nbsp;Title 2</h4><p>Lorem ipsum dolor sit amet, consectetur adipiscing elit,</p></li>
                        <li class="ellipsis"><h4 class="dark"><i class="fa fa-newspaper-o"></i>&nbsp;Title 3</h4><p>Lorem ipsum dolor sit amet, consectetur adipiscing elit,</p></li>
                        <li class="ellipsis"><h4 class="dark"><i class="fa fa-newspaper-o"></i>&nbsp;Title 4</h4><p>Lorem ipsum dolor sit amet, consectetur adipiscing elit,</p></li>
                    </ul>
                </div>

休眠键和值的计数

4 个答案: