improve sql parser, support sql server

src/main/java/com/alibaba/druid/sql/ast/statement/SQLAlterTableDropColumnItem.java

@@ -15,6 +15,9 @@
  */
 package com.alibaba.druid.sql.ast.statement;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.ast.SQLObjectImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
@@ -22,22 +25,22 @@ import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 public class SQLAlterTableDropColumnItem extends SQLObjectImpl implements SQLAlterTableItem {
 
     private static final long serialVersionUID = 1L;
-    private SQLName           columnName;
+    private List<SQLName>     columns          = new ArrayList<SQLName>();
+
+    public SQLAlterTableDropColumnItem(){
+
+    }
 
     @Override
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {
-            acceptChild(visitor, columnName);
+            acceptChild(visitor, columns);
         }
         visitor.endVisit(this);
     }
 
-    public SQLName getColumnName() {
-        return columnName;
-    }
-
-    public void setColumnName(SQLName columnName) {
-        this.columnName = columnName;
+    public List<SQLName> getColumns() {
+        return columns;
     }
 
 }

src/main/java/com/alibaba/druid/sql/ast/statement/SQLColumnDefinition.java

@@ -27,13 +27,13 @@ import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 @SuppressWarnings("serial")
 public class SQLColumnDefinition extends SQLObjectImpl implements SQLTableElement {
 
-    private SQLName                         name;
-    private SQLDataType                     dataType;
-    private SQLExpr                         defaultExpr;
-    private final List<SQLColumnConstraint> constaints = new ArrayList<SQLColumnConstraint>(0);
-    private String                          comment;
+    protected SQLName                         name;
+    protected SQLDataType                     dataType;
+    protected SQLExpr                         defaultExpr;
+    protected final List<SQLColumnConstraint> constaints = new ArrayList<SQLColumnConstraint>(0);
+    protected String                          comment;
 
-    private Boolean                         enable;
+    protected Boolean                         enable;
 
     public SQLColumnDefinition(){
 

src/main/java/com/alibaba/druid/sql/ast/statement/SQLCreateIndexStatement.java

@@ -20,6 +20,7 @@ import java.util.List;
 
 import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.ast.SQLStatementImpl;
+import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class SQLCreateIndexStatement extends SQLStatementImpl implements SQLDDLStatement {
 
@@ -36,10 +37,14 @@ public class SQLCreateIndexStatement extends SQLStatementImpl implements SQLDDLS
 
     private String                     type;
 
+    public SQLCreateIndexStatement(){
+
+    }
+
     public SQLTableSource getTable() {
         return table;
     }
-    
+
     public void setTable(SQLName table) {
         this.setTable(new SQLExprTableSource(table));
     }
@@ -72,4 +77,13 @@ public class SQLCreateIndexStatement extends SQLStatementImpl implements SQLDDLS
         this.type = type;
     }
 
+    @Override
+    protected void accept0(SQLASTVisitor visitor) {
+        if (visitor.visit(this)) {
+            acceptChild(visitor, getName());
+            acceptChild(visitor, getTable());
+            acceptChild(visitor, getItems());
+        }
+        visitor.endVisit(this);
+    }
 }

src/main/java/com/alibaba/druid/sql/ast/statement/SQLPrimaryKeyImpl.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 1999-2011 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.druid.sql.ast.statement;
+
+import com.alibaba.druid.sql.visitor.SQLASTVisitor;
+
+@SuppressWarnings("serial")
+public class SQLPrimaryKeyImpl extends SQLUnique implements SQLPrimaryKey {
+
+    @Override
+    protected void accept0(SQLASTVisitor visitor) {
+        if (visitor.visit(this)) {
+            acceptChild(visitor, this.getName());
+            acceptChild(visitor, this.getColumns());
+        }
+        visitor.endVisit(this);
+    }
+}

src/main/java/com/alibaba/druid/sql/ast/statement/SQLUnique.java

@@ -26,6 +26,10 @@ public class SQLUnique extends SQLConstaintImpl implements SQLUniqueConstraint,
 
     private final List<SQLExpr> columns = new ArrayList<SQLExpr>();
 
+    public SQLUnique(){
+
+    }
+
     public List<SQLExpr> getColumns() {
         return columns;
     }