improved odps sql parser, support more 'change column' syntax.

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

@@ -17,10 +17,12 @@
 package com.alibaba.druid.sql.ast.statement;
 
 import com.alibaba.druid.sql.ast.SQLExpr;
+import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.ast.SQLObjectImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class SQLAlterTableAlterColumn extends SQLObjectImpl implements SQLAlterTableItem {
+    private SQLName             originColumn;
 
     private SQLColumnDefinition column;
 
@@ -81,4 +83,14 @@ public class SQLAlterTableAlterColumn extends SQLObjectImpl implements SQLAlterT
         this.dropDefault = dropDefault;
     }
 
+    public SQLName getOriginColumn() {
+        return originColumn;
+    }
+
+    public void setOriginColumn(SQLName originColumn) {
+        if (originColumn != null) {
+            originColumn.setParent(this);
+        }
+        this.originColumn = originColumn;
+    }
 }

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

@@ -42,6 +42,9 @@ public class SQLAlterTableRenameColumn extends SQLObjectImpl implements SQLAlter
     }
 
     public void setColumn(SQLName column) {
+        if (column != null) {
+            column.setParent(this);
+        }
         this.column = column;
     }
 
@@ -50,6 +53,9 @@ public class SQLAlterTableRenameColumn extends SQLObjectImpl implements SQLAlter
     }
 
     public void setTo(SQLName to) {
+        if (to != null) {
+            to.setParent(this);
+        }
         this.to = to;
     }