1.很多时候我们需要从数据库中获取指定表的所有列的相关属性，如 name,commens,datatype,datalength,pk等。下面就是制定的语句。

select c.TABLE_NAME TABLE_CODE,           t.comments TABLE_NAME,           C.COLUMN_NAME COL_CODE,           c2.comments COL_NAME,           c.DATA_TYPE COL_TYPE,            decode(c.NULLABLE,'N','1','0') NULLABLE,           c.DATA_LENGTH,           c.DATA_PRECISION,           decode(PK.COLUMN_NAME, null, '0', '1') pk      from user_tab_columns c      left join user_tab_comments t        on c.TABLE_NAME = t.TABLE_NAME      join user_col_comments c2        on c2.table_name = c.TABLE_NAME       and c2.column_name = c.COLUMN_NAME      LEFT JOIN (select cu.table_name, CU.column_name                   from user_cons_columns cu, user_constraints au                  where cu.constraint_name = au.constraint_name                    and au.constraint_type = 'P'                    and au.table_name = '表名') PK        ON PK.COLUMN_NAME = C.COLUMN_NAME     where c.Table_Name = '表名'     order by c.COLUMN_ID asc

下面是语句运行结果