查询oracle表结构，字段，字段类型长度，字段注释

SELECT distinct b.column_name
,b.data_type
,b.data_length
,a.comments
FROM user_col_comments a
,all_tab_columns b
WHERE a.table_name = b.table_name and b.column_name=a.column_name and
a.table_name = ‘表名’;