NonUniqueResultException: query did not return a unique result: 2 error when returning attributes for collection of items in DB

I am trying to read a set of answers that a user submits to a database. The table has the following columns: PKid, clientId, questionId, answer, archived. Client submissions populate in this manner to decrease the footprint of what would otherwise be a very large table:

Whenever I try to access this data to display in the frontend, I get this error, and this is the full stack trace:

org.springframework.dao.IncorrectResultSizeDataAccessException: query did not return a unique result: 2 at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:382) ~[spring-orm-6.0.12.jar:6.0.12] at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:234) ~[spring-orm-6.0.12.jar:6.0.12] at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:550) ~[spring-orm-6.0.12.jar:6.0.12] at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61) ~[spring-tx-6.0.12.jar:6.0.12] at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:243) ~[spring-tx-6.0.12.jar:6.0.12] at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:152) ~[spring-tx-6.0.12.jar:6.0.12] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12] at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:135) ~[spring-data-jpa-3.0.10.jar:3.0.10] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12] at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) ~[spring-aop-6.0.12.jar:6.0.12] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12] at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:244) ~[spring-aop-6.0.12.jar:6.0.12] at jdk.proxy10/jdk.proxy10.$Proxy1065.getQuestionText(Unknown Source) ~[na:na] at com.example.demo.QuestionOptions.QuestionOptionsService.getQuestionText(QuestionOptionsService.java:80) ~[classes/:0.0.1-SNAPSHOT] at com.example.demo.Submissions.SubmissionsService.getSubmissionByCID(SubmissionsService.java:38) ~[classes/:0.0.1-SNAPSHOT] at com.example.demo.Submissions.SubmissionsController.getSubmissionByCID(SubmissionsController.java:30) ~[classes/:0.0.1-SNAPSHOT] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na] at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na] at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343) ~[spring-aop-6.0.12.jar:6.0.12] at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:699) ~[spring-aop-6.0.12.jar:6.0.12] at com.example.demo.Submissions.SubmissionsController$$SpringCGLIB$$0.getSubmissionByCID(<generated>) ~[classes/:0.0.1-SNAPSHOT] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na] at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na] at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:118) ~[spring-webmvc-6.0.12.jar:6.0.12] at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:884) ~[spring-webmvc-6.0.12.jar:6.0.12] at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-6.0.12.jar:6.0.12] at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-6.0.12.jar:6.0.12] at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1081) ~[spring-webmvc-6.0.12.jar:6.0.12] at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:974) ~[spring-webmvc-6.0.12.jar:6.0.12] at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1011) ~[spring-webmvc-6.0.12.jar:6.0.12] at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) ~[spring-webmvc-6.0.12.jar:6.0.12] at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) ~[servlet-api.jar:6.0] at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.0.12.jar:6.0.12] at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[servlet-api.jar:6.0] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-websocket.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:110) ~[spring-web-6.0.12.jar:6.0.12] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.springframework.security.web.FilterChainProxy.lambda$doFilterInternal$3(FilterChainProxy.java:231) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:365) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.access.intercept.AuthorizationFilter.doFilter(AuthorizationFilter.java:100) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:126) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:120) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:131) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:85) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:100) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:179) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilterInternal(BasicAuthenticationFilter.java:170) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at com.example.demo.JwtTokenFilter.doFilterInternal(JwtTokenFilter.java:62) ~[classes/:0.0.1-SNAPSHOT] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:107) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:93) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:90) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:75) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.context.SecurityContextHolderFilter.doFilterInternal(SecurityContextHolderFilter.java:69) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:62) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.session.DisableEncodeUrlFilter.doFilterInternal(DisableEncodeUrlFilter.java:42) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:233) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:191) ~[spring-security-web-6.0.0.jar:6.0.0] at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:352) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:268) ~[spring-web-6.0.12.jar:6.0.12] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.springframework.session.web.http.SessionRepositoryFilter.doFilterInternal(SessionRepositoryFilter.java:143) ~[spring-session-core-3.0.3.jar:3.0.3] at org.springframework.session.web.http.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:82) ~[spring-session-core-3.0.3.jar:3.0.3] at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:352) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:268) ~[spring-web-6.0.12.jar:6.0.12] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.springframework.boot.web.servlet.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:124) ~[spring-boot-3.0.11.jar:3.0.11] at org.springframework.boot.web.servlet.support.ErrorPageFilter$1.doFilterInternal(ErrorPageFilter.java:99) ~[spring-boot-3.0.11.jar:3.0.11] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.boot.web.servlet.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:117) ~[spring-boot-3.0.11.jar:3.0.11] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.0.12.jar:6.0.12] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.12.jar:6.0.12] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[catalina.jar:10.1.17] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[catalina.jar:10.1.17] at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[catalina.jar:10.1.17] at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[catalina.jar:10.1.17] at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) ~[catalina.jar:10.1.17] at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[catalina.jar:10.1.17] at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[catalina.jar:10.1.17] at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:673) ~[catalina.jar:10.1.17] at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[catalina.jar:10.1.17] at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:340) ~[catalina.jar:10.1.17] at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391) ~[tomcat-coyote.jar:10.1.17] at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-coyote.jar:10.1.17] at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896) ~[tomcat-coyote.jar:10.1.17] at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1744) ~[tomcat-coyote.jar:10.1.17] at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-coyote.jar:10.1.17] at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-util.jar:10.1.17] at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-util.jar:10.1.17] at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-util.jar:10.1.17] at java.base/java.lang.Thread.run(Thread.java:840) ~[na:na] Caused by: jakarta.persistence.NonUniqueResultException: query did not return a unique result: 2 at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:128) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final] at org.hibernate.query.spi.AbstractSelectionQuery.getSingleResult(AbstractSelectionQuery.java:466) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final] at org.springframework.data.jpa.repository.query.JpaQueryExecution$SingleEntityExecution.doExecute(JpaQueryExecution.java:193) ~[spring-data-jpa-3.0.10.jar:3.0.10] at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:90) ~[spring-data-jpa-3.0.10.jar:3.0.10] at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:148) ~[spring-data-jpa-3.0.10.jar:3.0.10] at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:136) ~[spring-data-jpa-3.0.10.jar:3.0.10] at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:136) ~[spring-data-commons-3.0.10.jar:3.0.10] at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:120) ~[spring-data-commons-3.0.10.jar:3.0.10] at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:164) ~[spring-data-commons-3.0.10.jar:3.0.10] at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:143) ~[spring-data-commons-3.0.10.jar:3.0.10] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12] at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:72) ~[spring-data-commons-3.0.10.jar:3.0.10] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12] at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-6.0.12.jar:6.0.12] at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:391) ~[spring-tx-6.0.12.jar:6.0.12] at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-6.0.12.jar:6.0.12] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12] at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) ~[spring-tx-6.0.12.jar:6.0.12] ... 127 common frames omitted

The reason this occurs is because it is trying to return a unique value, when the very concept of the transaction precludes it. I don't know what part of the code is causing it.

Table design:

Model:

@Entity
@Table(name = "submissions")
public class Submissions {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "subid")
    private int subid;
    
    @Column(name="cid")
    private int cid;
    
    @Column(name = "qid")
    private int qid;
    
    @Column(name = "answer")
    private String answer;
    
    @Column(name = "archived")
    private String archived;

// getters/setters, etc...

Controller method:

        @PreAuthorize("hasRole('ROLE_USER')")
    @GetMapping("/get-submission-by-client-id")
    public List<Map<String, Object>> getSubmissionByCID(@RequestParam("cid") Integer cid) {
        return submissionService.getSubmissionByCID(cid);       
    }

Service method:

        @Autowired
    SubmissionsRepository submissionsRepo;
    
    @Autowired
    QuestionOptionsService qoService;

        public List<Map<String, Object>> getSubmissionByCID(Integer cid) {
        
        
        List <Object[]> qList =  submissionsRepo.getSubmissionByCID(cid);
            
        List<Map<String, Object>> resultList = new ArrayList<>();
        
        for (Object[] array : qList) {
            System.out.println("Printing out item: " + Arrays.toString(array));
            
            Integer qid = (Integer) array[0];     
            System.out.println("Qid after being insulated is : " + qid);
            
            String questionText = qoService.getQuestionText(qid);
            String answer = (String) array[1];
            
            Map<String, Object> qaMap = new HashMap<>();
            qaMap.put("Question", questionText);
            qaMap.put("Answer", answer);
            resultList.add(qaMap);
            
            System.out.println("The question text is: " + questionText);
        }
        System.out.println("Result List is: " + resultList);
        return resultList;
    }

Repository method:

        @Query(value = "SELECT qid, answer FROM dbo.submissions WHERE cid = :cid", nativeQuery = true)
    List<Object[]> getSubmissionByCID(@Param("cid") Integer cid);

This is the most similar question I could find:Link

It focuses on method consistency for returning a collection, but in my case, I account for that and I need an Object, because I need to separately refer these attributes for the frontend part.

I also have this exact same set up for another table in the application, which is organized in exactly the same way, without a problem.I've compared this code to the relevant other parts of the application that do the same thing, and they work fine.

Thinking it might be database corruption, I recreated the relevant table, to no effect.

In any case, I'd appreciate insight into what the problem might be. Thank you!

@MKSHRI, you were right to point me in this direction. The issue was ultimately a duplicated ID for a question in the questions table:

And then, to solve it, I ran this query to offset the remaining id's by 1:

UPDATE questionstable
SET qid = qid + 1 WHERE qid >= 178

The code is from this link: Link

And now the output is indeed the relevant client data that shows up correctly.