SQL查询与MySQL

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我正在使用Jesey在Java(JAX-RS)中实现Restful Web Service.我在Tomcat v7.0上运行它我使用Hibernate将数据映射到数据库(MysqL).我有一个查询来获取可交付成果列表： 
  1. deliverables = (List<Deliverable>) session.createQuery("Select deliverable from
  2.                 Task as t where t.project.id= :id And t.user.username = :name")
  3.     .setLong("id",projectId).setString("name",username).list();

它给了我一百个可交付成果,但我希望在Task表中有TOP三.我感谢任何帮助.我该如何修改查询？

请注意,这三个可交付成果不应重复.

与@FGreg的答案存在冲突.当我使用这些查询时,一切正常：

  1. deliverables = (List<Deliverable>) session.createQuery(
  2.     "from Deliverable as d where d.project.id= :id").setLong("id",projectId).list();
  3.     long task_id;
  4.     for(Deliverable d: deliverables) {
  5.         task_id =  (long) session.createQuery("Select Max(id) from Task as t where     
  6.         t.deliverable.id = :id and t.user.username = :name")
  7.         .setLong("id",d.getId()).setString("name",username).uniqueResult();
  8.          d.setTask_id(task_id);
  9.     }
  10.     sortDeliverable(deliverables);   // sort by Task_id

我认为在@FGreg提供的查询中,不考虑max(id),例如,task_id = 31,643使用了两次可交付成果.可能会认为Task_id = 31,这是错误的.有任何帮助来解决它吗？

我试过没有明显的@FGreg查询.然后它除了重复问题以外工作正常.

我试过这个：

  1. deliverables = (List<Deliverable>) session.createQuery("from Deliverable as d inner join 
  2.  Task as t where t.id = (select max(t1.id) from Task as t1 where t1.deliverable.id = d.id)   
  3.  and d.project.id= :id and t.user.username = :name order by t.id desc")
  4.                     .setMaxResults(3)
  5.                     .setLong("id",projectId)
  6.                     .setString("name",username)
  7.                     .list();

我在堆栈跟踪中得到了New Error：

  1. Jul 13,2012 5:03:10 PM org.hibernate.hql.internal.ast.ErrorCounter reportError
  2. ERROR:  Path expected for join!
  3. Jul 13,2012 5:03:10 PM org.hibernate.hql.internal.ast.ErrorCounter reportError
  4. ERROR:  Path expected for join!
  5.  Path expected for join!
  6.     at org.hibernate.hql.internal.ast.HqlsqlWalker.createFromJoinElement(HqlsqlWalker.java:371)
  7.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.joinElement(HqlsqlBaseWalker.java:3477)
  8.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.fromElement(HqlsqlBaseWalker.java:3263)
  9.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.fromElementList(HqlsqlBaseWalker.java:3141)
  10.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.fromClause(HqlsqlBaseWalker.java:694)
  11.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.query(HqlsqlBaseWalker.java:550)
  12.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.selectStatement(HqlsqlBaseWalker.java:287)
  13.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.statement(HqlsqlBaseWalker.java:235)
  14.     at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:248)
  15.     at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:183)
  16.     at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
  17.     at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:101)
  18.     at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
  19.     at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:119)
  20.     at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:214)
  21.     at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:192)
  22.     at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1537)
  23.     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  24.     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  25.     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  26.     at java.lang.reflect.Method.invoke(Unknown Source)
  27.     at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:350)
  28.     at $Proxy65.createQuery(Unknown Source)
  29.     at se.softwerk.timelog.controller.DeliverableManager.deliverableList2(DeliverableManager.java:185)
  30.     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  31.     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  32.     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  33.     at java.lang.reflect.Method.invoke(Unknown Source)
  34.     at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
  35.     at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ResponSEOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:205)
  36.     at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
  37.     at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288)
  38.     at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
  39.     at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
  40.     at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
  41.     at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
  42.     at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469)
  43.     at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400)
  44.     at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
  45.     at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
  46.     at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
  47.     at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
  48.     at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:708)
  49.     at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
  50.     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
  51.     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
  52.     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
  53.     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
  54.     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
  55.     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
  56.     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
  57.     at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:928)
  58.     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
  59.     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
  60.     at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
  61.     at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:539)
  62.     at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:298)
  63.     at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
  64.     at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
  65.     at java.lang.Thread.run(Unknown Source)
  66.  
  67. Jul 13,2012 5:03:10 PM org.hibernate.hql.internal.ast.ErrorCounter reportError
  68. ERROR:  Invalid path: 't.id'
  69. Jul 13,2012 5:03:10 PM org.hibernate.hql.internal.ast.ErrorCounter reportError
  70. ERROR:  Invalid path: 't.id'
  71.  Invalid path: 't.id'
  72.     at org.hibernate.hql.internal.ast.util.LiteralProcessor.lookupConstant(LiteralProcessor.java:131)
  73.     at org.hibernate.hql.internal.ast.tree.DotNode.resolve(DotNode.java:219)
  74.     at org.hibernate.hql.internal.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:118)
  75.     at org.hibernate.hql.internal.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:114)
  76.     at org.hibernate.hql.internal.ast.HqlsqlWalker.resolve(HqlsqlWalker.java:883)
  77.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.expr(HqlsqlBaseWalker.java:1246)
  78.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.exprOrSubquery(HqlsqlBaseWalker.java:4252)
  79.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.comparisonExpr(HqlsqlBaseWalker.java:3730)
  80.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.logicalExpr(HqlsqlBaseWalker.java:1923)
  81.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.logicalExpr(HqlsqlBaseWalker.java:1848)
  82.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.logicalExpr(HqlsqlBaseWalker.java:1848)
  83.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.whereClause(HqlsqlBaseWalker.java:782)
  84.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.query(HqlsqlBaseWalker.java:583)
  85.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.selectStatement(HqlsqlBaseWalker.java:287)
  86.     at org.hibernate.hql.internal.antlr.HqlsqlBaseWalker.statement(HqlsqlBaseWalker.java:235)
  87.     at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:248)
  88.     at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:183)
  89.     at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
  90.     at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:101)
  91.     at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
  92.     at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:119)
  93.     at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:214)
  94.     at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:192)
  95.     at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1537)
  96.     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  97.     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  98.     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  99.     at java.lang.reflect.Method.invoke(Unknown Source)
  100.     at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:350)
  101.     at $Proxy65.createQuery(Unknown Source)
  102.     at se.softwerk.timelog.controller.DeliverableManager.deliverableList2(DeliverableManager.java:185)
  103.     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  104.     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  105.     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  106.     at java.lang.reflect.Method.invoke(Unknown Source)

模型类：

  1. @Entity
  2. public class Task {
  3.  
  4.     @Id
  5.     @GeneratedValue
  6.     private long id;
  7.  
  8.     @ManyToOne(optional = false)
  9.     private User user;
  10.  
  11.     @ManyToOne(optional = false)
  12.     private Project project;
  13.  
  14.  
  15.     @ManyToOne(optional = false)
  16.     private Deliverable deliverable;
  17. }

并且可交付：

  1. @Entity
  2. public class Deliverable {
  3.  
  4.     @Id
  5.     @GeneratedValue
  6.     private long id;
  7.  
  8.     @Column(name = "short",nullable = false)
  9.     private String key;
  10.  
  11.     @Column(nullable = false)
  12.     private String name;
  13.  
  14.     @OneToMany(targetEntity = Task.class,mappedBy = "deliverable",fetch = FetchType.LAZY,cascade = CascadeType.ALL)
  15.     @JsonIgnore
  16.     private Collection<Task> tasks;
  17.  
  18.     @ManyToOne(optional = false,fetch = FetchType.EAGER)
  19.     @JoinColumn(name = "project")
  20.     private Project project;
  21.  
  22.     @ManyToOne(fetch = FetchType.EAGER)
  23.     @JoinColumn(name = "parent")
  24.     private Deliverable parent;
  25.  
  26.     @OneToMany(targetEntity = Deliverable.class,mappedBy = "parent",cascade = CascadeType.ALL)
  27.     @JsonIgnore
  28.     private Collection<Deliverable> children;
  29. }

解决方法

我想你要求按ID排序的前3个可交付成果.你可以尝试这样的事情：

编辑：好的,我会再多拿一次.这应该为您提供由Task.id订购的前3个可交付物,仅获取与max相关的Deliverable(Task.id)

  1. deliverables = 
  2.         (List<Deliverable>) session.createQuery(
  3.             "from Deliverable as d,Task as t
  4.                 where t.deliverable.id = d.id and
  5.                 t.id = (select max(t1.id) from Task t1 where t1.deliverable.id = d.id)
  6.                 and d.project.id= :id
  7.                 and t.user.username = :name
  8.                 order by t.id desc")
  9.         .setMaxResults(3)
  10.         .setLong("id",projectId)
  11.         .setString("name",username)
  12.         .list();

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