堅持如何在 spring 數據應用程序中找到 QueryDSL 謂詞

Question

我在查詢一些數據時遇到問題，我將簡要解釋我的問題並舉例說明

我使用 Spring 數據、QueryDSL 和 MySQL。

我想在 queryDSL 方法中這樣查詢。 一個具體的例子只是一個簡單的例子來給出一個想法。

例如，有兩個表 Employee 和 Certificate。 兩者之間的關系是 ONE（員工）到 MANY（證書）

以下是表格

Employee (id, first_name, last_name);
Certificate (id, name, date, fk_emp);

以下是實體，

@Entity
@Table(name = "EMPLOYEE")
class Employee {
  @Id
  @Column(name = "ID")
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;

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

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

  @OneToMany(mappedBy = "employee", cascade = CascadeType.ALL)
  private List<Certificate> certificates = new ArrayList<>();
}

@Entity
@Table(name = "CERTIFICATE")
class Certificate {
  @Id
  @Column(name = "ID")
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;

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

  @Column(name = "DATE")
  private Date date;

  @ManyToOne
  @JoinColumn(name = "REF_EMPLOYEE")
  private Employee employee;
}

QueryDSL 謂詞應該是什么來返回所有姓名包含（在名字和姓氏中）的員工以及從日期在 22-12-2014 到 22-12-2015 之間認證的結果

同時，我想獲得所有沒有任何證書的員工

結果示例：

+----+--------------------+---------------------+--------+
| id | name               | date                | fk_emp |
+----+--------------------+---------------------+--------+
|  1 | FirstName LastName | 2014-02-01 00:00:00 |  11111 |
+----+--------------------+---------------------+--------+
|  2 | FirstName LastName | 2014-03-01 00:00:00 |  null  |
+----+--------------------+---------------------+--------+
|  3 | FirstName LastName | 2014-04-01 00:00:00 |        |
+----+--------------------+---------------------+--------+
|  5 | FirstName LastName | 2014-05-01 00:00:00 |        |
+----+--------------------+---------------------+--------+
| 12 | FirstName LastName | 2014-06-01 00:00:00 |  25555 |
+----+--------------------+---------------------+--------+
| 13 | FirstName LastName | 2014-07-01 00:00:00 |  78888 |
+----+--------------------+---------------------+--------+
| 16 | FirstName LastName | 2014-08-01 00:00:00 |  null  |
+----+--------------------+---------------------+--------+

謝謝

Answer 1

原生 JPQL 查詢：

SELECT * FROM EMPLOYEE A
LEFT JOIN CERTIFICATE B ON A.ID = B.REF_EMPLOYEE AND DATE BETWEEN CAST('2014-12-22' AS DATE) AND CAST('2015-12-22' AS DATE);

Querydsl 連接變體：

query.from(employee)
    .leftJoin(employee.certificates, certificate)
    .on(certificate.date.between('from_date', 'to_date'))
    .list(employee);

注意：這里的日期格式可以不同，請根據您的需要更改