记
目的:
遇到这种情况,mysql to oracle时 text类型转到oracle自动变为BLOB,但这些字段只需要CLOB.所以打算把BLOB转为CLOB。(在sqlplu或plsql中完成)
解决办法
例:表gw_gift 字段description BLOB
1、增加字段description1 CLOB
2、把BLOB列数据写入CLOB
update gw_gift p set p.description1=utl_raw.cast_to_varchar2(p.description) where DBMS_LOB.GETLENGTH(DESCRIPTION)>2000;
commit;
注:utl_raw.cast_to_varchar2() 转换BLOB为RAW,再转入CLOB
DBMS_LOB.GETLENGTH()取得BLOB内容的长度。因为BLOB转RAW时超过2000会报“ORA-22835:缓冲区对于BLOB到RAW转换而言太小(实际:4366,最大2000)”
当遇到BLOB值大于2000时的解决办法:
一、如果大于2000的行不多,先转换小于2000的,再手工修改大于2000的。
二、利用function函数完成
1.新建BLOB to CLOB的function
CREATE OR REPLACE FUNCTION blob_to_clob (blob_in IN BLOB) RETURN CLOB
AS
v_clob CLOB;
v_varchar VARCHAR2(32767);
v_start PLS_INTEGER := 1;
v_buffer PLS_INTEGER := 32767;
tmp_num number;
BEGIN
DBMS_LOB.CREATETEMPORARY(v_clob, TRUE);
tmp_num := CEIL(DBMS_LOB.GETLENGTH(blob_in) / v_buffer);
if tmp_num > 0 then --防止传入的BLOB为NULL或长度为0时引发错误
FOR i IN 1..tmp_num
LOOP
v_varchar := UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(blob_in, v_buffer, v_start));
DBMS_LOB.WRITEAPPEND(v_clob, LENGTH(v_varchar), v_varchar);
v_start := v_start + v_buffer;
END LOOP;
end if;
RETURN v_clob;
END blob_to_clob;
2.调用blob_to_clob 来完成转换
update gs_gift p set p.description1=blob_to_clob(p.description);
commit;
3、删除description列,修改CLOB的description1 列名为description
完成!
列:
--------------------------------
CREATE OR REPLACE FUNCTION blob_to_clob (blob_in IN BLOB) RETURN CLOB
AS
v_clob CLOB;
v_varchar VARCHAR2(32767);
v_start PLS_INTEGER := 1;
v_buffer PLS_INTEGER := 32767;
tmp_num number;
BEGIN
DBMS_LOB.CREATETEMPORARY(v_clob, TRUE);
tmp_num := CEIL(DBMS_LOB.GETLENGTH(blob_in) / v_buffer);
if tmp_num > 0 then --防止传入的BLOB为NULL或长度为0时引发错误
FOR i IN 1..tmp_num
LOOP
v_varchar := UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(blob_in, v_buffer, v_start));
DBMS_LOB.WRITEAPPEND(v_clob, LENGTH(v_varchar), v_varchar);
v_start := v_start + v_buffer;
END LOOP;
end if;
RETURN v_clob;
END blob_to_clob;
commit;
--GS_AUTHORIZATIONAPPLY
ALTER TABLE GS_AUTHORIZATIONAPPLY ADD AUDITREMARK1 CLOB;--新增
update GS_AUTHORIZATIONAPPLY g set g.AUDITREMARK1=blob_to_clob(g.AUDITREMARK);--转换
commit;
alter table GS_AUTHORIZATIONAPPLY drop column AUDITREMARK;--删除
alter table GS_AUTHORIZATIONAPPLY rename column AUDITREMARK1 to AUDITREMARK;--重命名列
--GS_CUSTOMER
ALTER TABLE GS_CUSTOMER ADD INTRO1 CLOB;--新增
update GS_CUSTOMER g set g.INTRO1=blob_to_clob(g.INTRO);--转换
commit;
alter table GS_CUSTOMER drop column INTRO;--删除
alter table GS_CUSTOMER rename column INTRO1 to INTRO;--重命名列
--GS_CUSTOMERCONTACTTASK
ALTER TABLE GS_CUSTOMERCONTACTTASK ADD INTRO1 CLOB;--新增
update GS_CUSTOMERCONTACTTASK g set g.INTRO1=blob_to_clob(g.INTRO);--转换
commit;
alter table GS_CUSTOMERCONTACTTASK drop column INTRO;--删除
alter table GS_CUSTOMERCONTACTTASK rename column INTRO1 to INTRO;--重命名列
--GS_CUSTOMERVISITRECORD
ALTER TABLE GS_CUSTOMERVISITRECORD ADD INTRO1 CLOB;--新增
update GS_CUSTOMERVISITRECORD g set g.INTRO1=blob_to_clob(g.INTRO);--转换
commit;
alter table GS_CUSTOMERVISITRECORD drop column INTRO;--删除
alter table GS_CUSTOMERVISITRECORD rename column INTRO1 to INTRO;--重命名列
--GS_DIARY
ALTER TABLE GS_DIARY ADD CONTENT1 CLOB;--新增
update GS_DIARY g set g.CONTENT1=blob_to_clob(g.CONTENT);--转换
commit;
alter table GS_DIARY drop column CONTENT;--删除
alter table GS_DIARY rename column CONTENT1 to CONTENT;--重命名列
--gs_gift
ALTER TABLE gs_gift ADD description1 CLOB;--新增
update gs_gift g set g.description1=blob_to_clob(g.description);--转换
commit;
alter table gs_gift drop column description;--删除
alter table gs_gift rename column description1 to description;--重命名列
--gw_gift
ALTER TABLE gw_gift ADD description1 CLOB;--新增
update gw_gift g set g.description1=blob_to_clob(g.description);--转换
commit;
alter table gw_gift drop column description;--删除
alter table gw_gift rename column description1 to description;--重命名列
drop function blob_to_clob;--删除function
---------------------------------------------