MemoryQueryResult getColumnIndex throw exception when using Oracle database
## Bug Report

when execute Oracle's DQL, getting the result throws an exception
```
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
	at java.util.ArrayList.rangeCheck(ArrayList.java:657)
	at java.util.ArrayList.get(ArrayList.java:433)
	at org.apache.shardingsphere.core.execute.sql.execute.result.QueryResultMetaData.getColumnIndex(QueryResultMetaData.java:140)
	at org.apache.shardingsphere.core.execute.sql.execute.result.MemoryQueryResult.getValue(MemoryQueryResult.java:95)
	at org.apache.shardingsphere.core.merge.dql.common.StreamMergedResult.getValue(StreamMergedResult.java:56)
	at org.apache.shardingsphere.core.merge.dql.common.DecoratorMergedResult.getValue(DecoratorMergedResult.java:46)
	at org.apache.shardingsphere.shardingjdbc.jdbc.core.resultset.ShardingResultSet.getString(ShardingResultSet.java:141)
	at org.hibernate.type.descriptor.sql.VarcharTypeDescriptor$2.doExtract(VarcharTypeDescriptor.java:62)
	at org.hibernate.type.descriptor.sql.BasicExtractor.extract(BasicExtractor.java:47)
	at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:261)
	at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:257)
	at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:247)
	at org.hibernate.type.AbstractStandardBasicType.hydrate(AbstractStandardBasicType.java:333)
	at org.hibernate.loader.Loader.extractKeysFromResultSet(Loader.java:794)
	at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:719)
	at org.hibernate.loader.Loader.processResultSet(Loader.java:991)
	at org.hibernate.loader.Loader.doQuery(Loader.java:949)
	at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:341)
	at org.hibernate.loader.Loader.doList(Loader.java:2692)
	at org.hibernate.loader.Loader.doList(Loader.java:2675)
	at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2507)
	at org.hibernate.loader.Loader.list(Loader.java:2502)
	at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:502)
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:392)
	at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:216)
	at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1490)
	at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1445)
	at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1414)
	at org.hibernate.query.Query.getResultList(Query.java:146)
	at org.hibernate.query.criteria.internal.compile.CriteriaQueryTypeQueryAdapter.getResultList(CriteriaQueryTypeQueryAdapter.java:72)
	at org.springframework.data.jpa.repository.support.SimpleJpaRepository.readPage(SimpleJpaRepository.java:570)
	at org.springframework.data.jpa.repository.support.SimpleJpaRepository.findAll(SimpleJpaRepository.java:389)
	at org.springframework.data.jpa.repository.support.SimpleJpaRepository.findAll(SimpleJpaRepository.java:357)
	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.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:377)
	at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:200)
	at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:641)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:605)
	at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:590)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:294)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:135)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
	at com.sun.proxy.$Proxy88.findAll(Unknown Source)
	at com.fudabd.oracletest.controller.TerminalController.listTerminal(TerminalController.java:83)
	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:209)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:891)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:981)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:873)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:858)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)
```

### Which version of ShardingSphere did you use?

3.1.0 and 4.0.0-RC1-SNAPSHOT

### Which project did you use? Sharding-JDBC or Sharding-Proxy?

Sharding-JDBC

### Expected behavior

get results correctly

### Actual behavior

throw exception `java.lang.IndexOutOfBoundsException: Index: 0, Size: 0`

### Reason analyze (If you can)

MemoryQueryResult will get the table metadata when init, the columnLabel in oracle metadata is upper case. 
But the input of `getColumnIndex` method is lower case so that can't find the index.

### Steps to reproduce the behavior, such as: SQL to execute, sharding rule configuration, when exception occur etc.

1. clone example codes
2. change sharding-jdbc version to 3.1.0 or 4.0.0-RC1-SNAPSHOT
3. check configuration of jdbc at file `application-sharding-databases-oracle.properties`
4. run `OracleTestApplication`
5. visit http://localhost:8080/insertTest
6. visit http://localhost:8080/listTerminal

### Example codes for reproduce this issue (such as a github link).

https://github.com/fdlzp/sharding-jdbc_jpa_oracle

diff --git a/sharding-core/sharding-core-execute/src/main/java/org/apache/shardingsphere/core/execute/sql/execute/result/QueryResultMetaData.java b/sharding-core/sharding-core-execute/src/main/java/org/apache/shardingsphere/core/execute/sql/execute/result/QueryResultMetaData.java
index e40fcceedbf..4a47497162b 100644
--- a/sharding-core/sharding-core-execute/src/main/java/org/apache/shardingsphere/core/execute/sql/execute/result/QueryResultMetaData.java
+++ b/sharding-core/sharding-core-execute/src/main/java/org/apache/shardingsphere/core/execute/sql/execute/result/QueryResultMetaData.java
@@ -18,8 +18,6 @@
 package org.apache.shardingsphere.core.execute.sql.execute.result;
 
 import com.google.common.base.Optional;
-import com.google.common.collect.HashMultimap;
-import com.google.common.collect.Multimap;
 import lombok.SneakyThrows;
 import org.apache.shardingsphere.core.rule.ShardingRule;
 import org.apache.shardingsphere.core.rule.TableRule;
@@ -29,9 +27,9 @@ import org.apache.shardingsphere.spi.encrypt.ShardingEncryptor;
 
 import java.sql.ResultSetMetaData;
 import java.sql.SQLException;
-import java.util.ArrayList;
 import java.util.Collections;
-import java.util.Map.Entry;
+import java.util.Map;
+import java.util.TreeMap;
 
 /**
  * Query result meta data.
@@ -40,7 +38,7 @@ import java.util.Map.Entry;
  */
 public final class QueryResultMetaData {
     
-    private final Multimap<String, Integer> columnLabelAndIndexes;
+    private final Map<String, Integer> columnLabelAndIndexes;
     
     private final ResultSetMetaData resultSetMetaData;
     
@@ -62,9 +60,9 @@ public final class QueryResultMetaData {
     }
     
     @SneakyThrows
-    private Multimap<String, Integer> getColumnLabelAndIndexMap(final ResultSetMetaData resultSetMetaData) {
-        Multimap<String, Integer> result = HashMultimap.create();
-        for (int columnIndex = 1; columnIndex <= resultSetMetaData.getColumnCount(); columnIndex++) {
+    private Map<String, Integer> getColumnLabelAndIndexMap(final ResultSetMetaData resultSetMetaData) {
+        Map<String, Integer> result = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
+        for (int columnIndex = resultSetMetaData.getColumnCount(); columnIndex > 0; columnIndex--) {
             result.put(resultSetMetaData.getColumnLabel(columnIndex), columnIndex);
         }
         return result;
@@ -75,8 +73,9 @@ public final class QueryResultMetaData {
      * 
      * @return column count
      */
+    @SneakyThrows
     public int getColumnCount() {
-        return columnLabelAndIndexes.size();
+        return resultSetMetaData.getColumnCount();
     }
     
     /**
@@ -87,12 +86,7 @@ public final class QueryResultMetaData {
      */
     @SneakyThrows
     public String getColumnLabel(final int columnIndex) {
-        for (Entry<String, Integer> entry : columnLabelAndIndexes.entries()) {
-            if (columnIndex == entry.getValue()) {
-                return entry.getKey();
-            }
-        }
-        throw new SQLException("Column index out of range", "9999");
+        return resultSetMetaData.getColumnLabel(columnIndex);
     }
     
     /**
@@ -113,7 +107,7 @@ public final class QueryResultMetaData {
      * @return column name
      */
     public Integer getColumnIndex(final String columnLabel) {
-        return new ArrayList<>(columnLabelAndIndexes.get(columnLabel)).get(0);
+        return columnLabelAndIndexes.get(columnLabel);
     }
     
     /**
diff --git a/sharding-core/sharding-core-merge/src/main/java/org/apache/shardingsphere/core/merge/dql/DQLMergeEngine.java b/sharding-core/sharding-core-merge/src/main/java/org/apache/shardingsphere/core/merge/dql/DQLMergeEngine.java
index 486f4a5beea..376bf9cd335 100644
--- a/sharding-core/sharding-core-merge/src/main/java/org/apache/shardingsphere/core/merge/dql/DQLMergeEngine.java
+++ b/sharding-core/sharding-core-merge/src/main/java/org/apache/shardingsphere/core/merge/dql/DQLMergeEngine.java
@@ -101,7 +101,7 @@ public final class DQLMergeEngine implements MergeEngine {
     
     private Map<String, Integer> getColumnLabelIndexMap(final QueryResult queryResult) throws SQLException {
         Map<String, Integer> result = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
-        for (int i = 1; i <= queryResult.getColumnCount(); i++) {
+        for (int i = queryResult.getColumnCount(); i > 0; i--) {
             result.put(SQLUtil.getExactlyValue(queryResult.getColumnLabel(i)), i);
         }
         return result;
diff --git a/sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/PreparedStatementExecutorTest.java b/sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/PreparedStatementExecutorTest.java
index d7655be20cd..f16b15b1de1 100644
--- a/sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/PreparedStatementExecutorTest.java
+++ b/sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/PreparedStatementExecutorTest.java
@@ -78,6 +78,7 @@ public final class PreparedStatementExecutorTest extends AbstractBaseExecutorTes
         ResultSet resultSet = mock(ResultSet.class);
         ResultSetMetaData resultSetMetaData = mock(ResultSetMetaData.class);
         when(resultSetMetaData.getColumnName(1)).thenReturn("column");
+        when(resultSetMetaData.getColumnLabel(1)).thenReturn("column");
         when(resultSetMetaData.getTableName(1)).thenReturn("table_x");
         when(resultSetMetaData.getColumnCount()).thenReturn(1);
         when(resultSet.getString(1)).thenReturn("value");
@@ -95,6 +96,7 @@ public final class PreparedStatementExecutorTest extends AbstractBaseExecutorTes
         ResultSet resultSet2 = mock(ResultSet.class);
         ResultSetMetaData resultSetMetaData = mock(ResultSetMetaData.class);
         when(resultSetMetaData.getColumnName(1)).thenReturn("column");
+        when(resultSetMetaData.getColumnLabel(1)).thenReturn("column");
         when(resultSetMetaData.getTableName(1)).thenReturn("table_x");
         when(resultSetMetaData.getColumnCount()).thenReturn(1);
         when(resultSet1.getMetaData()).thenReturn(resultSetMetaData);
diff --git a/sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/StatementExecutorTest.java b/sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/StatementExecutorTest.java
index 424b3f7400e..058a9a90112 100644
--- a/sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/StatementExecutorTest.java
+++ b/sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/StatementExecutorTest.java
@@ -79,6 +79,7 @@ public final class StatementExecutorTest extends AbstractBaseExecutorTest {
         ResultSet resultSet = mock(ResultSet.class);
         ResultSetMetaData resultSetMetaData = mock(ResultSetMetaData.class);
         when(resultSetMetaData.getColumnName(1)).thenReturn("column");
+        when(resultSetMetaData.getColumnLabel(1)).thenReturn("column");
         when(resultSetMetaData.getTableName(1)).thenReturn("table_x");
         when(resultSetMetaData.getColumnCount()).thenReturn(1);
         when(resultSet.getString(1)).thenReturn("value");
@@ -97,6 +98,7 @@ public final class StatementExecutorTest extends AbstractBaseExecutorTest {
         ResultSet resultSet2 = mock(ResultSet.class);
         ResultSetMetaData resultSetMetaData = mock(ResultSetMetaData.class);
         when(resultSetMetaData.getColumnName(1)).thenReturn("column");
+        when(resultSetMetaData.getColumnLabel(1)).thenReturn("column");
         when(resultSetMetaData.getTableName(1)).thenReturn("table_x");
         when(resultSetMetaData.getColumnCount()).thenReturn(1);
         when(resultSet1.getMetaData()).thenReturn(resultSetMetaData);
['sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/PreparedStatementExecutorTest.java', 'sharding-core/sharding-core-merge/src/main/java/org/apache/shardingsphere/core/merge/dql/DQLMergeEngine.java', 'sharding-jdbc/sharding-jdbc-core/src/test/java/org/apache/shardingsphere/shardingjdbc/executor/StatementExecutorTest.java', 'sharding-core/sharding-core-execute/src/main/java/org/apache/shardingsphere/core/execute/sql/execute/result/QueryResultMetaData.java']