Oracle 中如何将 CLOB 转换为 BLOB？
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How convert CLOB to BLOB in Oracle?
提问by Ayan Kutkozhaev
Firstly I converted a BLOB of an image to CLOB, and then converted that CLOB back to BLOB. I cannot see the reconverted image. How can i solve this problem?
首先，我将图像的 BLOB 转换为 CLOB，然后将该 CLOB 转换回 BLOB。我看不到重新转换的图像。我怎么解决这个问题？
blob_to_clob function:
blob_to_clob 函数：
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;
BEGIN
DBMS_LOB.CREATETEMPORARY(v_clob, TRUE);
FOR i IN 1..CEIL(DBMS_LOB.GETLENGTH(blob_in) / v_buffer)
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;
RETURN v_clob;
END blob_to_clob;
clob_to_blob function:
clob_to_blob 函数：
CREATE OR REPLACE FUNCTION clob_to_blob2(p_clob IN CLOB) RETURN BLOB IS
v_blob BLOB;
v_offset NUMBER DEFAULT 1;
v_amount NUMBER DEFAULT 4096;
v_offsetwrite NUMBER DEFAULT 1;
v_amountwrite NUMBER;
v_buffer VARCHAR2(4096 CHAR);
BEGIN dbms_lob.createtemporary(v_blob, TRUE);
Begin
LOOP
dbms_lob.READ (lob_loc => p_clob,
amount => v_amount,
offset => v_offset,
buffer => v_buffer);
v_amountwrite := utl_raw.length (r => utl_raw.cast_to_raw(c => v_buffer));
dbms_lob.WRITE (lob_loc => v_blob,
amount => v_amountwrite,
offset => v_offsetwrite,
buffer => utl_raw.cast_to_raw(v_buffer));
v_offsetwrite := v_offsetwrite + v_amountwrite;
v_offset := v_offset + v_amount;
v_amount := 4096;
END LOOP;
EXCEPTION
WHEN no_data_found THEN
NULL;
End;
RETURN v_blob;
END clob_to_blob2;
回答by Nashev
Code like this will perform minimal recoding:
像这样的代码将执行最少的重新编码：
create or replace function clob2blob(AClob CLOB) return BLOB is
Result BLOB;
o1 integer;
o2 integer;
c integer;
w integer;
begin
o1 := 1;
o2 := 1;
c := 0;
w := 0;
DBMS_LOB.CreateTemporary(Result, true);
DBMS_LOB.ConvertToBlob(Result, AClob, length(AClob), o1, o2, 0, c, w);
return(Result);
end clob2blob;
/
But CLOB can not properly contain all Image data without any encoding like Base64
但是 CLOB 不能正确包含所有 Image 数据而没有像 Base64 这样的任何编码
