MyBatis TooManyResultsException: Expected one result but found multiple - Troubleshooting Guide

{/'title/':/'org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 2//n//tat org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:80) ~[mybatis-3.5.6.jar:3.5.6]//n//tat java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]//n//tat java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]//n//tat java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]//n//tat java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]//n//tat org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:427) ~[mybatis-spring-2.0.6.jar:2.0.6]//n//tat com.sun.proxy.$Proxy73.selectOne(Unknown Source) ~[na:na]//n//tat org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:160) ~[mybatis-spring-2.0.6.jar:2.0.6]//n//tat com.baomidou.mybatisplus.core.override.MybatisMapperMethod.execute(MybatisMapperMethod.java:108) ~[mybatis-plus-core-3.3.2.jar:3.3.2]//n//tat com.baomidou.mybatisplus.core.override.MybatisMapperProxy.invoke(MybatisMapperProxy.java:96) ~[mybatis-plus-core-3.3.2.jar:3.3.2]//n//tat com.sun.proxy.$Proxy80.selectOne(Unknown Source) ~[na:na]//n//tat com.example.mybatisplus.service.impl.UserServiceImpl.login(UserServiceImpl.java:32) ~[classes/:na]//n//tat com.example.mybatisplus.service.impl.UserServiceImpl$$FastClassBySpringCGLIB$$bd5f7487.invoke() ~[classes/:na]//n//tat org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.3.28.jar:5.3.28]//n//tat org.springframework.aop.framework.CglibAopProxy.invokeMethod(CglibAopProxy.java:386) ~[spring-aop-5.3.28.jar:5.3.28]//n//tat org.springframework.aop.framework.CglibAopProxy.access$000(CglibAopProxy.java:85) ~[spring-aop-5.3.28.jar:5.3.28]//n//tat org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:704) ~[spring-aop-5.3.28.jar:5.3.28]//n//tat com.example.mybatisplus.service.impl.UserServiceImpl$$EnhancerBySpringCGLIB$$54511c1e.login() ~[classes/:na]//n//tat com.example.mybatisplus.web.controller.UserController.login(UserController.java:91) ~[classes/:na]//n//tat java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]//n//tat java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]//n//tat java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]//n//tat java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]//n//tat org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-5.3.28.jar:5.3.28]//n//tat org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.28.jar:5.3.28]//n//tat org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:965) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat javax.servlet.http.HttpServlet.service(HttpServlet.java:555) ~[tomcat-embed-core-9.0.76.jar:4.0.FR]//n//tat org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.28.jar:5.3.28]//n//tat javax.servlet.http.HttpServlet.service(HttpServlet.java:623) ~[tomcat-embed-core-9.0.76.jar:4.0.FR]//n//tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:209) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.28.jar:5.3.28]//n//tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.28.jar:5.3.28]//n//tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.28.jar:5.3.28]//n//tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.28.jar:5.3.28]//n//tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.28.jar:5.3.28]//n//tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.28.jar:5.3.28]//n//tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:481) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:390) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:926) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1791) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.76.jar:9.0.76]//n//tat java.base/java.lang.Thread.run(Thread.java:829) ~[na:na]//n/',/'在MyBatis中，当使用selectOne()方法执行查询时，期望返回一个结果或者返回null，但是实际查询结果返回了多个结果，导致抛出TooManyResultsException异常。//n//n可能的原因有：//n1. SQL语句存在错误，导致查询结果返回了多个匹配的记录。//n2. 数据库中存在重复的数据，导致查询结果返回了多个相同的记录。//n//n解决方法：//n1. 检查SQL语句是否正确，确保查询条件准确无误。//n2. 检查数据库中是否存在重复的数据，如果有必要，可以进行数据清理或者添加唯一约束来避免重复数据的产生。//n3. 如果查询结果确实可能返回多个结果，可以考虑使用selectList()方法来执行查询，返回一个结果列表。//n4. 如果只需要第一个结果，可以使用limit关键字限制查询结果的数量。//n//n请根据具体情况进行排查和处理。/