HQL (九) 连接查询

http://wlh269.iteye.com/blog/322050

连接查询（重要）
* 内连接
* 外连接（左连接/右连接）
参见：JoinQueryTest.java

内连接有三种：inner join ，join，“=”

Java代码

1. packagecom.wlh.hibernate;
3. importjava.util.Iterator;
4. importjava.util.List;
6. importjunit.framework.TestCase;
8. importorg.hibernate.Session;
10. publicclassJoinQueryTestextendsTestCase{
12. /**
13. *内联结
14. */
15. publicvoidtestQuery1(){
16. Sessionsession=null;
17. try{
18. session=HibernateUtils.getSession();
19. session.beginTransaction();
20. //====关键字join==========//
21. Liststudents=session.createQuery("selects.name,c.namefromStudentsjoins.classesc").list();
22. for(Iteratoriter=students.iterator();iter.hasNext();){
23. Object[]o=(Object[])iter.next();
24. System.out.println("id="+o[0]+",o[1]"+o[0]);
25. }
26. session.getTransaction().commit();
27. }catch(Exceptione){
28. e.printStackTrace();
29. session.getTransaction().rollback();
30. }finally{
31. HibernateUtils.closeSession(session);
32. }
33. }
35. /**
36. *内联结
37. */
38. publicvoidtestQuery2(){
39. Sessionsession=null;
40. try{
41. session=HibernateUtils.getSession();
42. session.beginTransaction();
43. //=======关键字innerjoin默认就是内连接，所以inner可以加上，也可以省略======//
44. Liststudents=session.createQuery("selects.name,c.namefromStudentsinnerjoins.classesc").list();
45. for(Iteratoriter=students.iterator();iter.hasNext();){
46. Object[]o=(Object[])iter.next();
47. System.out.println("id="+o[0]+",o[1]"+o[0]);
48. }
49. session.getTransaction().commit();
50. }catch(Exceptione){
51. e.printStackTrace();
52. session.getTransaction().rollback();
53. }finally{
54. HibernateUtils.closeSession(session);
55. }
56. }
58. /**
59. *内联结
60. */
61. publicvoidtestQuery3(){
62. Sessionsession=null;
63. try{
64. session=HibernateUtils.getSession();
65. session.beginTransaction();
66. //===========用"="实现内联===========//
67. Liststudents=session.createQuery("selects.name,c.namefromStudents,Classescwheres.classes.id=c.id").list();
68. for(Iteratoriter=students.iterator();iter.hasNext();){
69. Object[]o=(Object[])iter.next();
70. System.out.println("id="+o[0]+",o[1]"+o[0]);
71. }
72. session.getTransaction().commit();
73. }catch(Exceptione){
74. e.printStackTrace();
75. session.getTransaction().rollback();
76. }finally{
77. HibernateUtils.closeSession(session);
78. }
79. }
82. [b][color=red]外联接：能够查出2个表之间不相互关联的记录[/color][/b]
85. <PREclass=javaname="code"></PRE>
86. <BR>
87. <BR>/**
88. <BR>*外联结
89. <BR>*/
90. <BR>publicvoidtestQuery4(){
91. <BR>Sessionsession=null;
92. <BR>try{
93. <BR>session=HibernateUtils.getSession();
94. <BR>session.beginTransaction();
95. <BR>//查询出所有的学生（包括没有班级的学生）
96. <BR>Liststudents=session.createQuery("selects.name,c.namefromStudentsleftjoins.classesc").list();
97. <BR>for(Iteratoriter=students.iterator();iter.hasNext();){
98. <BR>Object[]o=(Object[])iter.next();
99. <BR>System.out.println("id="+o[0]+",o[1]="+o[1]);
100. <BR>}
101. <BR>session.getTransaction().commit();
102. <BR>}catch(Exceptione){
103. <BR>e.printStackTrace();
104. <BR>session.getTransaction().rollback();
105. <BR>}finally{
106. <BR>HibernateUtils.closeSession(session);
107. <BR>}
108. <BR>}
109. <BR>
110. <BR>
111. <BR>
112. <BR>/**
113. <BR>*外联结
114. <BR>*/
115. <BR>publicvoidtestQuery5(){
116. <BR>Sessionsession=null;
117. <BR>try{
118. <BR>session=HibernateUtils.getSession();
119. <BR>session.beginTransaction();
120. <BR>//查询出所有的班级，（包括没有学生的班级）
121. <BR>Liststudents=session.createQuery("selects.name,c.namefromStudentsrightjoins.classesc").list();
122. <BR>for(Iteratoriter=students.iterator();iter.hasNext();){
123. <BR>Object[]o=(Object[])iter.next();
124. <BR>System.out.println("id="+o[0]+",o[1]="+o[1]);
125. <BR>}
126. <BR>session.getTransaction().commit();
127. <BR>}catch(Exceptione){
128. <BR>e.printStackTrace();
129. <BR>session.getTransaction().rollback();
130. <BR>}finally{
131. <BR>HibernateUtils.closeSession(session);
132. <BR>}
133. <BR>}
134. <BR>
135. <BR>
136. <BR>}