您需要使用 DBMS_LOB.createtemporary:

You need to create a temporary blob with DBMS_LOB.createtemporary:

SQL> CREATE OR REPLACE FUNCTION CONCAT_BLOB(A IN BLOB, B IN BLOB) RETURN BLOB IS
  2     C BLOB;
  3  BEGIN
  4     dbms_lob.createtemporary(c, TRUE);
  5     DBMS_LOB.APPEND(c, A);
  6     DBMS_LOB.APPEND(c, B);
  7     RETURN c;
  8  END;
  9  /

Function created

那么你应该可以在更新语句中使用它:

Then you should be able to use it in an update statement:

SQL> CREATE TABLE t (a BLOB, b BLOB, c BLOB);

Table created

SQL> INSERT INTO t VALUES
  2     (utl_raw.cast_to_raw('aaa'), utl_raw.cast_to_raw('bbb'), NULL);

1 row inserted

SQL> UPDATE t SET c=CONCAT_BLOB(a,b);

1 row updated

SQL> SELECT utl_raw.cast_to_varchar2(a),
  2         utl_raw.cast_to_varchar2(b),
  3         utl_raw.cast_to_varchar2(c)
  4  FROM t;

UTL_RAW.CAST_TO_VARCHAR2(A UTL_RAW.CAST_TO_VARCHAR2(B UTL_RAW.CAST_TO_VARCHAR2(C
-------------------------- -------------------------- --------------------------
aaa                        bbb                        aaabbb