oracle10g - 将当前 CLOB 列复制到 Oracle 中的新 BLOB 列

Question

我有一张 table ，上面有 CLOB列。我想将现有数据转换为 BLOB数据类型。失败了 ORA-252858 invalid alteration of datatype .

我想创建一个新的 BLOB列，将现有数据复制到其中，然后删除现有 CLOB列。

如何从 CLOB 复制列到 BLOB柱子？

Answer 1

create table temp(col_clob clob,col_blob blob);

insert into temp (col_clob) values('hi i am gaurav soni');
insert into temp (col_clob) values('hi i am gaurav soni');
insert into temp (col_clob) values('hi i am gaurav soni');
insert into temp (col_clob) values('hi i am gaurav soni');
insert into temp (col_clob) values('hi i am gaurav soni');

/你需要创建一个函数，将clob转换为blob，如下所示:
坦率地说，我从另一个来源获取了这个功能，但你会感到困惑，因为在那个论坛上有一个讨论，这就是为什么我在这里提到/

create or replace function CLOB_TO_BLOB (p_clob CLOB) return BLOB
as
 l_blob          blob;
 l_dest_offset   integer := 1;
 l_source_offset integer := 1;
 l_lang_context  integer := DBMS_LOB.DEFAULT_LANG_CTX;
 l_warning       integer := DBMS_LOB.WARN_INCONVERTIBLE_CHAR;
BEGIN

  DBMS_LOB.CREATETEMPORARY(l_blob, TRUE);
  DBMS_LOB.CONVERTTOBLOB
  (
   dest_lob    =>l_blob,
   src_clob    =>p_clob,
   amount      =>DBMS_LOB.LOBMAXSIZE,
   dest_offset =>l_dest_offset,
   src_offset  =>l_source_offset,
   blob_csid   =>DBMS_LOB.DEFAULT_CSID,
   lang_context=>l_lang_context,
   warning     =>l_warning
  );
  return l_blob;
END;

--update the col_blob with the function we have created above 

 update temp set col_blob = clob_to_blob(col_clob);

select * from temp; 

输出

 COL_CLOB                               COL_BLOB           
-------------------------------------- -------------------
hi i am gaurav soni                    hi i am gaurav soni
hi i am gaurav soni                    hi i am gaurav soni
hi i am gaurav soni                    hi i am gaurav soni
hi i am gaurav soni                    hi i am gaurav soni
hi i am gaurav soni                    hi i am gaurav soni