JPQL中是否有这样的CASE表达式? [英] Is there such thing CASE expression in JPQL?

问题描述

假设有一张桌子:

TableA:Field1, Field2, Field3

和相关的 JPA 实体类

and associated JPA entity class

@Entity
@Table(name="TableA")
public class TableA{
  @Id
  @Column(name="Field1")
  private Long id;

  @Column(name="Field2")
  private Long field2;

  @Column(name="Field3")
  private Long field3;

  //... more associated getter and setter...
}

有没有什么方法可以构造一条JPQL语句，松散地翻译成这条SQL，即如何将case表达式翻译成JPQL?

Is there any way to construct a JPQL statement that loosely translated to this SQL, ie how to translated the case expression to JPQL?

select field1,
case
  when field2 = 1 then 'One'
  when field2 = 2 then 'Two'
  else 'Other number'
end,
field3
from tableA;

推荐答案

已在 JPA 2.0 中添加

It has been added in JPA 2.0

用法:

SELECT e.name, CASE WHEN (e.salary >= 100000) THEN 1 WHEN (e.salary < 100000) THEN 2 ELSE 0 END FROM Employee e

参考: http://en.wikibooks.org/wiki/Java_Persistence/JPQL_BNF#New_in_JPA_2.0

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