该查询的休眠等效项是什么（添加两列）

Question

This is the query

SELECT id, name, sub1, sub2, sub1 + sub2 AS total 
FROM mytable 
ORDER BY sub1 + sub2 ASC

What I am trying to do here is that I will add sub1 and sub2 and the result would be named TOTAL, and I will use TOTAL for Order By. so far this is how I've come up with but it is not rendering proper reults

sess().createSQLQuery("SELECT *, SUB1+ SUB2 AS TOTAL FROM TRACKS order by TOTAL ").addEntity(Student.class).list();

What is the hibernate or Query Criteria equivalent of what I am trying to do?

Answer 1

there is no such operation in JPQL, But what you could do is do a native query as follows:

"SELECT * FROM TRACKS order by SUB1+ SUB2"

And make a getter like:

public Double getTotal(){ //Replace Double for the data type you use
    return sub1 + sub2;
}

That way you could order the query as you want.

Is this what you're trying to do? I'm not sure if I understood quite well your question

Answer 2

I would say, that you have two options: Mapping or custom OrderBy object.

1) Mapping: If the Total would be used often, you can extend your entity mapping and create calculated/readonly property (seee 5.1.11. Property ):

<property name="total" formula="(sub1 + sub2)" insert="false" udpate="false" />

Now, we can use this value for Order by easily (and anywhere):

Criteria criteria = session.createCriteria(MyClass.class);
...
criteria.addOrder(Order.asc("total"));

2) We are still in the OOP world. The criteria.addOrder() operation, expects the Order object instance. So we can pass the Custom one: 'MyOrder'. In our case, it could be object accepting any valid SQL statement and directly inject that into ORDER BY:

public class MyOrder extends Order {
    public MyOrder(String propertyName, boolean ascending) {
        super(propertyName, ascending);
    }

    public String toSqlString(Criteria criteria, CriteriaQuery criteriaQuery) {
        StringBuilder fragment = new StringBuilder();
        fragment.append(propertyName );
        fragment.append( ascending ? " asc" : " desc" );
        return fragment.toString();
    }
}

Now, we can inject any (valid) SQL Script into ORDER BY this way:

Criteria criteria = session.createCriteria(MyClass.class);
...
criteria.addOrder(new MyOrder("(sub1 + sub2)", true));