如何在 HQL 中使用 sql case 子句？

Question

I really need help regarding this one.

Here is the code snippet:

  hSql=" select case 
      when min(start_day_plan) is not NULL then min(start_day_plan)
      else to_date((min(insertDate)) - cast('1 month' as interval),'yyyy-MM-dd' )
      end 
      from Project"

    getHibernateTemplate().find(hSql);

But this generates the error below:

---

java.lang.IllegalStateException: No data type for node: org.hibernate.hql.ast.tree.CaseNode 
 \-[CASE] CaseNode: 'case'
    +-[WHEN] SqlNode: 'when'
    |  +-[IS_NOT_NULL] UnaryLogicOperatorNode: 'is not null'
    |  |  \-[AGGREGATE] AggregateNode: 'min'
    |  |     \-[IDENT] IdentNode: 'start_day_plan' {originalText=start_day_plan}
    |  \-[AGGREGATE] AggregateNode: 'min'
    |     \-[IDENT] IdentNode: 'start_day_plan' {originalText=start_day_plan}
    \-[ELSE] SqlNode: 'else'
       \-[METHOD_CALL] MethodNode: '('
          +-[METHOD_NAME] IdentNode: 'to_date' {originalText=to_date}
          \-[EXPR_LIST] SqlNode: 'exprList'
             +-[MINUS] BinaryArithmeticOperatorNode: '-' {dataType=org.hibernate.type.DoubleType@bb21ab}
             |  +-[AGGREGATE] AggregateNode: 'min'
             |  |  \-[IDENT] IdentNode: 'insertDate' {originalText=insertDate}
             |  \-[METHOD_CALL] MethodNode: '('
             |     +-[METHOD_NAME] IdentNode: 'cast' {originalText=cast}
             |     \-[EXPR_LIST] SqlNode: 'exprList'
             |        +-[QUOTED_STRING] LiteralNode: ''1 month''
             |        \-[IDENT] IdentNode: 'interval' {originalText=interval}
             \-[QUOTED_STRING] LiteralNode: ''yyyy-MM-dd''

what will be the correct query for this? im just trying to subtract 1 month from the insertdate.

If you could help, please do so..thanks :)

Answer 1

I had a similar problem and solution than Stephan . We use JPA annotations on the getter but the field name was starting with a capital (which is not a good practice anyway).

private Timestamp MyTime;
...
@Column(name = "MYTIME")
public Timestamp getMyTime() {
    return MyTime;
}

I think when Hibernate was resolving my field name based on the getter it was looking for a field named myTime but there was only MyTime . The problem was solved when I renamed the field with the correct camel case convention ( myTime )

Answer 2

I believe your forgot the table you want to query.

     select 
       case 
         when min(start_day_plan) is not NULL then min(start_day_plan) 
         else to_date((min(insertDate)) - cast('1 month' as interval),'yyyy-MM-dd' ) 
       end
     from MyTable

Answer 3

I stumble upon this same problem recently. My error came from the fact JPA expects the same fields name in the query AND in the entity class.

@Entity
public class Foo {
  private String field1;
  ...
}

In the query field1 is expected and not Field1 nor FIELD1 and so on ...