做个笔记，仅供参考
SELECT d.TABLE_NAME tbName,//表名 COALESCE(t.COMMENTS, ' ') tbDesc, //表注释 a.COLUMN_NAME columnName, //字段名 a.DATA_TYPE columnType, //字段类型 a.DATA_LENGTH width, //字段长度 a.DATA_SCALE precision,//字段小数位 decode(a.NULLABLE,'Y','0','1') notNull,//是否允许空 COALESCE(m.COMMENTS, ' ') comments, //字段备注 decode(k.uniqueness,'UNIQUE','1','0') uniques, //是否唯一 COALESCE(k.index_name, ' ') indexName,//如果是索引，索引名 decode(k.key,'Y','1','0') masterKey//是否主键 FROM user_tab_columns a INNER JOIN user_tables d on a.TABLE_NAME=d.TABLE_NAME LEFT JOIN user_tab_comments t ON t.TABLE_NAME=d.TABLE_NAME LEFT JOIN user_col_comments m ON m.COLUMN_NAME=a.COLUMN_NAME AND m.TABLE_NAME=d.TABLE_NAME LEFT JOIN ( SELECT e.index_name,u.TABLE_NAME,u.COLUMN_NAME,e.uniqueness,decode(p.constraint_name,NULL,'N','Y') key from user_indexes e INNER JOIN user_ind_columns u ON e.index_name=u.index_name LEFT JOIN ( select constraint_name from user_constraints where constraint_type='P' ) p ON e.index_name=p.constraint_name ) k ON k.TABLE_NAME=a.TABLE_NAME and k.COLUMN_NAME=a.COLUMN_NAME ORDER BY tbName
备注：user_开头是当前用户，all_开头所有用户，dba_开头包括系统表
