oracle查询特定表字段、字段说明的sql

SELECT 
  a.TABLE_NAME 表名, 
  a.COLUMN_NAME 列名, 
  a.DATA_TYPE 数据类型, 
  a.DATA_LENGTH 长度, 
  b.COMMENTS 注释
FROM user_tab_columns a
LEFT JOIN user_col_comments b ON a.TABLE_NAME = b.TABLE_NAME AND a.COLUMN_NAME = b.COLUMN_NAME
WHERE a.TABLE_NAME = 'xxx'
ORDER BY a.COLUMN_ID