達夢數據庫是個國產數據庫，據說對Oracle有很好的兼容，本人親自從Oracle11g遷移到達夢6.0的數據庫上來，遇到一些問題，以下是問題記錄：

1。字段名錯誤

雖然達夢SQL可以兼容字段大小寫，但是JDVC實際上執行與Oracle會有差別，

達夢的ＳＱＬ可以執行，但是返回的字段的列名仍然按ＳＱＬ的大小寫返回，而Oracle會變成全部的大寫返回，

select typeid, typename from T_PUB_PRODUCT_TYPE

在用oracle執行后返回的列名叫TYPEID,TYPENAME

達夢返回值則為typeid,typename

比較好的做法是在數據庫執行語句之前，強制所有語句轉大寫：

rs = stmt.executeQuery(strSql.toUpperCase());??? //達夢數據庫對列名區分大小寫，Oracle會自動全轉大寫

==============================================

cuont(*)數據類型錯誤

語句：

select count(*) counts? from t_cus_product left join t_pub_product_type on p_type=typeid where p_createrid=200

oracle的count(*)可以兼容BigDecimal，達夢的count(*)是Long型

//count = ((BigDecimal)mapCount.get("counts")).intValue();//Orcale 為 BigDecimal

count = ((Long)mapCount.get("counts")).intValue();?? //達夢數據庫為Long

=====================================================

2。達夢數據庫語法關鍵字錯誤

以下語句oracle 可以執行，達夢卻報錯誤

select c.contractid,CONTRACTNO, c.contractname, c.type, sum,begin,end

state, userid, serviceid,P_NAME

from t_contract c

left join T_CUS_PRODUCT

on c.PRODUCTID=P_ID

where userid=200 order by contractid

原因：begin，end為達夢的保留關鍵字，語句修改為雙引號的形式，可以通過：

select c.contractid,CONTRACTNO, c.contractname, c.type, sum,"begin","end"

state, userid, serviceid,P_NAME

from t_contract c

left join T_CUS_PRODUCT

on c.PRODUCTID=P_ID

where userid=200 order by contractid

=============================================

3。查詢dual表報錯,

語句：select seq_c006_message_content.nextval from dual

java報錯：

java.sql.SQLException: 無效的表或視圖名 'dual'

at dm.jdbc.dbaccess.DBError.throwSQLException(Unknown Source)

at dm.jdbc.driver.DmdbCSI.prepareSQL(Unknown Source)

at dm.jdbc.driver.DmdbStatement.directExec(Unknown Source)

at dm.jdbc.driver.DmdbStatement.executeQuery(Unknown Source)

at cn.org.hz.common.dao.DBAccess.queryOneRow(DBAccess.java:110)

at cn.org.hz.blh.i007.I007Blh.I007MessageAdd(I007Blh.java:136)

at cn.org.hz.blh.i007.I007Blh$$FastClassByCGLIB$$f90d5dcf.invoke()

at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)

at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:700)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)

at cn.org.hz.common.aop.AroundInterceptor.invoke(AroundInterceptor.java:13)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)

at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:635)

at cn.org.hz.blh.i007.I007Blh$$EnhancerByCGLIB$$67fbf5f5.I007MessageAdd()

at cn.org.hz.ctrl.i007.I007Ctrl.I007MessageAdd(I007Ctrl.java:113)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.springframework.web.servlet.mvc.multiaction.MultiActionController.invokeNamedMethod(MultiActionController.java:473)

at org.springframework.web.servlet.mvc.multiaction.MultiActionController.handleRequestInternal(MultiActionController.java:410)

at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)

at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:875)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:809)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571)

at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:511)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)

at cn.org.hz.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:23)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)

at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)

at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)

at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)

at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)

at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)

at java.lang.Thread.run(Thread.java:619)

解決在本用戶下建立一個dual同義詞

如果需要直接訪問，可以用SYSDBA創建一個PUBLIC同義詞：

CREATE PUBLIC SYNONYM dual for SYSTEM.SYSDBA.SYSDUAL;

達夢雖然在sysdba下造了一個dual表來兼容oracle但是卻沒有在每個新用戶下建立同義詞，所有一般對dual表的查詢都會報錯。

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