oracel中自定义函数clob、blob转varchar2并截取。

关键字：
CLOB、BLOB、DBMS_LOB.SUBSTR、UTL_RAW.CAST_TO_VARCHAR2、
ORA-06502: PL/SQL: 数字或值错误 : raw variable length too long
ORA-06512: 在 line 1
、
ORA-01704

数据流处理过程中，由于DBMS_LOB.SUBSTRB，无法进行字节长度截取导致，经常遇到DBMS_LOB.SUBSTR截取长度依旧无法入库情况。通过自定义函数，精准截取指定长度。

clob_substrb

create or replace function clob_substrb(colb_str in clob,a in number,b in number) return varchar2 is
  str varchar2(32767);
begin
  str := DBMS_LOB.SUBSTR(colb_str, 32767, 1);
  str := substrb(str, a, b);
  return str;
exception
  when others then
    return NULL;
  
end;

blob_substrb

create or replace function blob_substrb(bolb_str in blob,a in number,b in number) return varchar2 is
  str varchar2(32767);
begin
  str := UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(bolb_str, 32767, 1));
  str := substrb(str, a, b);
  return str;
exception
  when others then
    return NULL;
  
end;