关键字: hibernate
使用SQLQuery
对原生SQL查询执行的控制是通过SQLQuery接口进行的，通过执行Session.createSQLQuery()获取这个接口。最简单的情况下，我们可以采用以下形式：
List cats
= sess.createSQLQuery(
" select * from cats
" ).addEntity(Cat.
class ).list();
= sess.createSQLQuery(
" select * from cats
" ).addEntity(Cat.
class ).list();
这个查询指定了:
SQL查询字符串
查询返回的实体
这里，结果集字段名被假设为与映射文件中指明的字段名相同。对于连接了多个表的查询，这就可能造成问题，因为可能在多个表中出现同样名字的字段。下面的方法就可以避免字段名重复的问题:
List cats
= sess.createSQLQuery(
" select {cat.*} from cats cat
" ).addEntity(
" cat
" , Cat. class
).list();
= sess.createSQLQuery(
" select {cat.*} from cats cat
" ).addEntity(
" cat
" , Cat. class
).list();
这个查询指定了:
SQL查询语句，它带一个占位符，可以让Hibernate使用字段的别名.
查询返回的实体，和它的SQL表的别名.
addEntity()方法将SQL表的别名和实体类联系起来，并且确定查询结果集的形态。
addJoin()方法可以被用于载入其他的实体和集合的关联.
List cats
= sess.createSQLQuery(
" select {cat.*}, {kitten.*} from cats cat, cats kitten where kitten.mother = cat.id
" )
.addEntity( "
cat " , Cat.
class )
.addJoin( "
kitten " ,
" cat.kittens
" )
.list();
= sess.createSQLQuery(
" select {cat.*}, {kitten.*} from cats cat, cats kitten where kitten.mother = cat.id
" )
.addEntity( "
cat " , Cat.
class )
.addJoin( "
kitten " ,
" cat.kittens
" )
.list();
原生的SQL查询可能返回一个简单的标量值或者一个标量和实体的结合体。
Double max =
(Double) sess.createSQLQuery(
" select max(cat.weight) as maxWeight from cats cat
" )
.addScalar( "
maxWeight "
, Hibernate.DOUBLE);
.uniqueResult();
(Double) sess.createSQLQuery(
" select max(cat.weight) as maxWeight from cats cat
" )
.addScalar( "
maxWeight "
, Hibernate.DOUBLE);
.uniqueResult();
除此之外，你还可以在你的hbm文件中描述结果集映射信息，在查询中使用。
List cats
= sess.createSQLQuery(
" select {cat.*}, {kitten.*} from cats cat, cats kitten where kitten.mother = cat.id
" )
.setResultSetMapping( "
catAndKitten "
)
.list();
= sess.createSQLQuery(
" select {cat.*}, {kitten.*} from cats cat, cats kitten where kitten.mother = cat.id
" )
.setResultSetMapping( "
catAndKitten "
)
.list();
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
>
- 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();
= sess.getNamedQuery(
" persons
" ).setString(
" namePattern
" , namePattern)
.setMaxResults( 50
)
.list();