16.2. 命名SQL查询

16.2. 命名SQL查询

可以在映射文档中定义查询的名字,然后就可以象调用一个命名的HQL查询一样直接调用命名SQL查询.在这种情况下,我们不需要调用addEntity()方法.

<sql-query name="persons">
    <return alias="person" class="eg.Person"/>
    SELECT person.NAME AS {person.name},
           person.AGE AS {person.age},
           person.SEX AS {person.sex}
    FROM PERSON person
    WHERE person.NAME LIKE :namePattern
</sql-query>

List people = sess.getNamedQuery("persons")
    .setString("namePattern", namePattern)
    .setMaxResults(50)
    .list();

<return-join>和 <load-collection> 元素是用来连接关联以及将查询定义为预先初始化各个集合的。

<sql-query name="personsWith">
    <return alias="person" class="eg.Person"/>
    <return-join alias="address" property="person.mailingAddress"/>
    SELECT person.NAME AS {person.name},
           person.AGE AS {person.age},
           person.SEX AS {person.sex},
           adddress.STREET AS {address.street},
           adddress.CITY AS {address.city},
           adddress.STATE AS {address.state},
           adddress.ZIP AS {address.zip}
    FROM PERSON person
    JOIN ADDRESS adddress
        ON person.ID = address.PERSON_ID AND address.TYPE='MAILING'
    WHERE person.NAME LIKE :namePattern
</sql-query>

一个命名查询可能会返回一个标量值.你必须使用<return-scalar>元素来指定字段的别名和 Hibernate类型

<sql-query name="mySqlQuery">
    <return-scalar column="name" type="string"/>
    <return-scalar column="age" type="long"/>
    SELECT p.NAME AS name,
           p.AGE AS age,
    FROM PERSON p WHERE p.NAME LIKE 'Hiber%'
</sql-query>

你可以把结果集映射的信息放在外部的<resultset>元素中，这样就可以在多个命名查询间，或者通过setResultSetMapping()API来访问。(此处原文即存疑。原文为：You can externalize the resultset mapping informations in a <resultset> element to either reuse them accross several named queries or through the setResultSetMapping() API.)

<resultset name="personAddress">
    <return alias="person" class="eg.Person"/>
    <return-join alias="address" property="person.mailingAddress"/>
</resultset>
<sql-query name="personsWith" resultset-ref="personAddress">
    SELECT person.NAME AS {person.name},
           person.AGE AS {person.age},
           person.SEX AS {person.sex},
           adddress.STREET AS {address.street},
           adddress.CITY AS {address.city},
           adddress.STATE AS {address.state},
           adddress.ZIP AS {address.zip}
    FROM PERSON person
    JOIN ADDRESS adddress
        ON person.ID = address.PERSON_ID AND address.TYPE='MAILING'
    WHERE person.NAME LIKE :namePattern
</sql-query>

另外,你可以在java代码中直接使用hbm文件中的结果集定义信息。

List cats = sess.createSQLQuery(
        "select {cat.*}, {kitten.*} from cats cat, cats kitten where kitten.mother = cat.id"
    )
    .setResultSetMapping("catAndKitten")
    .list();