例如對(duì)于TUser類
1.實(shí)體查詢
String hql = " from TUser";執(zhí)行這條語(yǔ)句會(huì)返回TUser以及TUser子類的紀(jì)錄。
hql = "from java.lang.Object"會(huì)返回?cái)?shù)據(jù)庫(kù)中所有庫(kù)表的紀(jì)錄。
where 語(yǔ)句
hql = "from TUser as user where user.name='yyy'";其中，as可以省略也一樣
hql = "from TUser user where user.name='yyy'";where子句中，我們可以通過(guò)比較運(yùn)算符設(shè)定條件，如：
=, <>, >, <, >=, <=, between, not between, in, not in, is, like等。
2.屬性查詢
List list = session.createQuery("select user.name, user.age from TUser as user").list();還可以在HQL中動(dòng)態(tài)構(gòu)造對(duì)象實(shí)例的方法，將數(shù)據(jù)封裝。
List list = session.createQuery("select new TUser(user.name, user.age) from TUser as user").list();
Iterator it = list.iterator();
while(it.hasNext() ) {
TUser user = (TUser)it.next();
System.out.println(user.getName());
}
但是要注意這里的TUser對(duì)象只是對(duì)name和age屬性的封裝，其他狀態(tài)均未賦值，所以不能用它來(lái)進(jìn)行更新操作。
也可以在HQL的Select子句中使用統(tǒng)計(jì)函數(shù)
"select count(*) ,min(user.age) from TUser as user"
也可以使用distinct關(guān)鍵字來(lái)刪除重復(fù)紀(jì)錄。
select distinct user.name from TUser as user;
3.實(shí)體的更新與刪除
hibernate 2中需要先查詢出實(shí)體，設(shè)置屬性后再保存。
hibernate 3中，提供了更靈活的方式(bulk delete/update)
更新：
Query query = session.createQuery("update TUser set age=18 where id=1");
query.executeUpdate();
刪除：
session.createQuery("delete TUser where age>=18");
query.executeUpdate();
4.分組與排序
Order by子句：
from TUser user order by user.name, user.age desc
Group by子句和Having子句
"select count(user), user.age from TUser user group by user.age having count(user)>10"
5.參數(shù)邦定
通過(guò)順序占位符?來(lái)填充參數(shù)：
1)hibernate 2 中通過(guò)session.find方法來(lái)填充
session.find("from TUser user where user.name=?", "Erica", Hibernate.STRING);
多個(gè)參數(shù)的情況：
Object[] args = new Object[] {"Erica", new Integer(20)};
Type[] types = new Type{Hibernate.STRING, Hibernate.INTEGER};
session.find("from TUser user where user.name=? and user.age=?", args, types);
2)通過(guò)Query接口進(jìn)行參數(shù)填充：
Query query = session.createQuery("from TUser user where user.name=? and user.age>?");
query.setString(0,"Erica");
query.setInteger(1, 20);
通過(guò)引用占位符來(lái)填充參數(shù)：
String hql = "from TUser where name=:name";
Query query = session.createQuery(hql);
query.setParameter("name","Erica");
甚至可以將查詢條件封裝為一個(gè)JavaBean
class UserQuery {
private String name;
private Integer age;
//getter and setter
}
String hql = "from TUser where name=:name and age=:age";
Query query = session.createQuery(hql);
UserQuery uq = new UserQuery();
uq.setName("Erica");
uq.setAge(new Integer(20));
query.setProperties(uq); //會(huì)調(diào)用里面的getter?
query.iterate();
6.聯(lián)合查詢
也可以使用 inner join,left outer join, right out join, full join
排列組合：form TUser, TAddress