Enter the following codes in MYSQL:
set sql_mode=‘STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION’;
Note:
if you use copy and paste, please delete the two single quotation marks and type them again, otherwise an error will be reported
if you enter them manually, there is no problem at all
You can’t specify target table for update in from clause in MySQL. This error means that you can’t select some values of the same table in the same SQL statement before updating the table. (not the same table)
Then execute to update the content of the first message of each user to Hello world
Because in the same SQL statement, select the minimum ID value of each user message in the message table first, and then update the message table, error 1093 (HY000): you can’t specify target table ‘message’ for update in from claim will appear.
Solution: select the result through an intermediate table again to avoid this error (including delete)
Modify after where condition
Note that only MySQL has this problem, and neither MSSQL nor Oracle has this problem.
I’m mysql8 For versions above 0, start to report errors when connecting to the MySQL database in the server with nodejs
This means that the server starts up, but there is an error in the password protocol in the database. The result I found on the Internet tells me that it is mysql8.0 supports a new cryptographic protocol, but nodejs does not support it at present.
The following is my solution after avoiding the pit, which may not be applicable to everyone
1. Log in to MySQL server
Open the command line as an administrator and enter
mysql -u administrator -p
If you are prompted that MySQL is not an executable file, you can CD on the command line to the bin directory in mysql, or add Mysql to the environment variable
Note: the above root is the user name you want to modify. It may not be administrator. Mine is administrator
2. Enter the password
Then enter the password and enter mysql
3. Select database
Therefore, first we need to select the database and enter it on the command line
use mysql
Note: This is mysql, not any other name, unless you modify the name of the table in the database where the user name and password are stored, but the probability is very small, and you can’t move there.
If the wrong database is selected, the following errors will be prompted in the subsequent password blank operation
4. Leave password blank
If the original password is not blank and the password is modified directly, an error will be reported
Password blank operation, enter
update user set authentication_string='' where user='administrator';
The above administrator is still the user name you need to modify the password protocol
5. Refresh
This step is important
flush privileges;
6. Modify password and agreement
I’ve been stuck in this step for a long time
When I modify the password agreement, the error in the figure appears
After checking a lot of information, I understand
Open the database, MySQL database and user table, and you can see
The host before the user name I want to modify is’% ‘instead of’ localhost ‘, so I need to change the localhost in the command to%
alter user 'administrator'@'%' identified with mysql_native_password by '123456';
The above administrator is the user name you need to change your password, and 123456 is your password
This completes all steps
MySQL forgot password modification, etc. many online tutorials don’t seem to apply to MySQL 8 0. Write this part when you have time.
Mysql Connect Error: Communications link failure:
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
Caused by: java.net.ConnectException: Connection refused: connect
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:828)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:448)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:241)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198)
at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:138)
at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:364)
at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:206)
at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:476)
at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:561)
at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:115)
at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112)
at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:265)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.startTransaction(AbstractPlatformTransactionManager.java:400)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:373)
at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:595)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:382)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:753)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:698)
at com.zj31mep.biz.system.service.impl.SysUserServiceImpl$$EnhancerBySpringCGLIB$$3489e14a.userLogin(<generated>)
at com.zj31mep.biz.common.controller.LoginController.userLogin(LoginController.java:31)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at com.zj31mep.biz.system.filter.LoginFilter.doFilter(LoginFilter.java:58)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at com.zj31mep.security.XssFilter.doFilter(XssFilter.java:25)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at com.zj31mep.security.CsrfFilter.doFilter(CsrfFilter.java:86)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.springframework.web.filter.CorsFilter.doFilterInternal(CorsFilter.java:91)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1722)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:89)
at com.mysql.cj.NativeSession.connect(NativeSession.java:120)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:948)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:818)
... 84 common frames omitted
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:156)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:63)
... 87 common frames omitted
[dev][ERROR] [2021-12-31 11:26:52.227] http-nio-9000-exec-2 com.zj31mep.exception.handler.GlobalExceptionHandler.handleException：37
Could not open JDBC Connection for transaction; nested exception is com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
org.springframework.transaction.CannotCreateTransactionException: Could not open JDBC Connection for transaction; nested exception is com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:309)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.startTransaction(AbstractPlatformTransactionManager.java:400)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:373)
at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:595)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:382)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:753)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:698)
at com.zj31mep.biz.system.service.impl.SysUserServiceImpl$$EnhancerBySpringCGLIB$$3489e14a.userLogin(<generated>)
at com.zj31mep.biz.common.controller.LoginController.userLogin(LoginController.java:31)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at com.zj31mep.biz.system.filter.LoginFilter.doFilter(LoginFilter.java:58)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at com.zj31mep.security.XssFilter.doFilter(XssFilter.java:25)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at com.zj31mep.security.CsrfFilter.doFilter(CsrfFilter.java:86)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.springframework.web.filter.CorsFilter.doFilterInternal(CorsFilter.java:91)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1722)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Caused by: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:828)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:448)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:241)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198)
at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:138)
at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:364)
at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:206)
at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:476)
at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:561)
at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:115)
at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112)
at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:265)
... 73 common frames omitted
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:89)
at com.mysql.cj.NativeSession.connect(NativeSession.java:120)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:948)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:818)
... 84 common frames omitted
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:156)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:63)
... 87 common frames omitted
[dev][WARN] [2021-12-31 11:26:52.603] http-nio-9000-exec-2 org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.logException：208
Resolved [org.springframework.transaction.CannotCreateTransactionException: Could not open JDBC Connection for transaction; nested exception is com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure<LF><LF>The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.]
2. Communications link failure solutions
The reason for the problem is that the MySQL connection JDBC URL has an error
For example, the correct port is 3306, but when configuring, it is configured as 3366, which can be corrected.
select orderNumber, sum(priceEach * quantityOrdered) as totalvalues from orderdetails where sum(priceEach * quantityOrdered) > 60000;
Error reporting reason:
This is because the aggregate function is used in the where statement.
Functions and differences between where and having:
Where is a constraint declaration that constrains the query conditions in the database before the result of the query is returned, that is, it works before the result is returned, and “aggregate function” cannot be used after where, because the execution order of where is before the aggregate function.
Having is a filtering declaration. Filtering is performed after the result of querying the database is returned, that is, it works after the result is returned, and “aggregation function” can be used after having. Note: having is used to filter the found results. You cannot use having for values that are not found. I always thought that having must be used together with group by. I tried it today. It’s just a screening condition. There’s no stress on binding.
Correct writing:
select orderNumber, sum(priceEach * quantityOrdered) as totalvalues from orderdetails group by orderNumber having sum(priceEach * quantityOrdered) > 60000;
Another thing to note is that SQL syntax:
SELECT [DISTINCT|DISINCTROW|ALL] select_ expression,… — Query results
[from table_references — specify the table to query
[where where_definition] – where clause, filter criteria for query data
[group by col_name,…]– Group the query results of [matching where clause]
[having where_definition] – conditionally restrict the grouped results
[order by {unsigned_integer | col_name | formula} [ASC | desc],…]– Sort query results
[limit [offset,] rows] – limit the number of displayed results
[procedure procedure_name] – query the result set data returned by the stored procedure
]
The writing order of query statements must follow the above rules.
1. Enter the container
Docker exec – it [MySQL container name]/bin/Bash
2. Log in to MySQL
mysql -uroot -p
Password: [enter your password] or enter directly
3. Execute the following command:
use MySQL;
4. Authorization
grant all privileges on ** to ‘root’@’%’ identified by ‘yourPassword’;
5. Refresh
Flush privileges;
Error Messages:
ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column ‘student.name’ which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
Check the version of MYSQL
select version();
View the Content in SQL_mode
select @@GLOBAL.sql_mode;
Reason:
The only_full_group_by option is enabled by default in mysql5.7 and above. My version is mysql5.7.27
Take a look at the syntax of group by:
select select the column in the group + aggregate function from the table name group by grouped column
From the perspective of grammatical format, the grouping is first established, and then the columns to be retrieved are determined. The columns to be retrieved can only be selected from the columns participating in the grouping.
My current Mysql version 5.7.27,
Let’s look at the meaning of ONLY_FULL_GROUP_BY: For the GROUP BY aggregation operation, if the column in the SELECT does not appear in the GROUP BY, then this SQL is illegal, because the column is not in the GROUP BY clause, that is to say, it is detected List
It must appear after the group by, otherwise an error will be reported, or this field appears in the aggregate function.
There are two solutions. The first is to temporarily solve the problem, which will reappear when the database is restarted, and the second is to modify the MySQL configuration file
Windows solution:
Method 1:
Delete ONLY_FULL_GROUP_BY in the queried sql_mode, it will be invalid after restart
set @@GLOBAL.sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
Method 2:
find your MySQL installation path first
select @@basedir;
Then go to the folder and find your my Ini configuration file, modify the content in [mysqld], add the following content, then exit the database and restart MySQL in the service
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
Linux solution:
Method 1:
Delete ONLY_FULL_GROUP_BY in the queried sql_mode, it will be invalid after restart
set @@GLOBAL.sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
Method 2:
The configuration file of mysql on linux is not called my.ini, the configuration file is in /etc/my.cnf
vim /etc/my.cnf
Modify the content in [mysqld], add the following content, and then restart mysql
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
Restart command:
service mysql restart
When linking MySQL database through pycharm, the query report will give an error prompt:
RuntimeError: ‘cryptography’ package is required for sha256_password or caching_sha2_password auth methods
Method 1: restart MySQL
① As an administrator, enter the command line “net start MySQL 80” in CMD (the service name of MySQL 80 is different here according to the installed version) to start mysql
② Enter “MySQL” to enter mysql.
③ pycharm runs again without reporting an error.
Method 2: install the cryptography package
Error: runtimeerror: ‘cryptography’ package is required for sha256_ password or caching_ sha2_ password auth methods
The error message means: sha256_Password and caching_sha2_ Password two encryption methods require cryptography.
Therefore, you only need to install the cryptography package: PIP install cryptography
① First, if you see mysql running in task manager. ② After opening cmd, enter the command "pip install cryptography", after successful installation, run pycharm again, no error is reported.
1. When calling an interface, an interface reports an error
o.s.b.f.xml. XmlBeanDefinitionReader: Loading XML bean definitions from class path resource [org/springframework/jdbc/support/sql-error-codes.xml]
o.s.jdbc. support. SQLErrorCodesFactory : SQLErrorCodes loaded: [DB2, Derby, H2, HSQL, Informix, MS-SQL, MySQL, Oracle, PostgreSQL, Sybase, Hana]
Screenshot information:
2. Solution ideas
(1) Look at the problem description, it is a database problem.
(2) Check the interface log, through the log, you can initially locate the problem in the “==> Preparing: REPLACE into” sql statement, while the log returned the sql statement’s input “==> Parameters”
(3) According to the parameters, the sql statement was executed in Navicat, and the result came out because of the problem of foreign keys in the database.
3.Summary
The problem how to solve is not the focus, the focus is to encounter such problems, first check the logs, locate where the problem, and then targeted to solve.
There are several common problems in the degree, such as field naming errors, type mismatch, data problems.
At the end of the day, according to the logs, execute the problem statement in the visual sql execution tool. The problem can be solved.
When using Mysql to execute update, if the primary key is not used in the where condition, the following error will be reported and the update cannot be executed.
Exception content: error code: 1175 You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column To disable safe mode, toggle the option in Preferences -> SQL Queries and reconnect.
Solution:
This is because MySql is running in safe-updates mode. Modify the database security mode to allow update or delete commands to be executed under non-primary key conditions.
Excuting an order:
SET SQL_SAFE_UPDATES = 0;