fix sqlserver select group by classcastException

src/test/java/com/alibaba/druid/sql/parser/SqlserverGroupByTest.java

@@ -0,0 +1,26 @@
+package com.alibaba.druid.sql.parser;
+
+import com.alibaba.druid.sql.ast.statement.SQLSelectStatement;
+import com.alibaba.druid.sql.dialect.sqlserver.parser.SQLServerStatementParser;
+import junit.framework.TestCase;
+import org.junit.Assert;
+
+/**
+ * Created by magicdoom on 2016/8/16.
+ */
+public class SqlserverGroupByTest extends TestCase
+{
+    public void testGroupBy() throws Exception {
+        String sql = "SELECT a.workflowid, COUNT(1) FROM workflow_base a GROUP BY a.workflowid";
+        SQLStatementParser parser = new SQLServerStatementParser(sql);
+        SQLSelectStatement stmt = (SQLSelectStatement) parser.parseStatement(); //
+        try {
+            stmt.toString();
+        }  catch (ClassCastException e)
+        {
+            Assert.fail(e.getMessage());
+        }
+
+
+    }
+}