.NET Core 查询Oracle BLOB字段报错：TTC Error

.NET Core NuGet程序包：Oracle.ManagedDataAccess.Core 查询Oracle BLOB字段报错：TTC Error解决方案

报错截图如下：

报错语句如下，其中PHOTO为BLOB字段：

select PHOTO from employee_photo

此类语句在.NET FrameWork下并无异常，但用.NET Core NuGet程序包：Oracle.ManagedDataAccess.Core访问Oracle数据库时爆发：TTC Error 异常 

后查找资料，官方并无解决方案，最后在：https://cloud.tencent.com/developer/ask/202816 找到相关答案

修改后SQL语句如下

WITH
INFO
AS
(
    SELECT
        dbms_lob.getlength(A.PHOTO) AS FILE_CONTENT_LENGTH, 
        MOD(dbms_lob.getlength(A.PHOTO),2000) AS MOD,
        CASE
            WHEN MOD(dbms_lob.getlength(A.PHOTO),2000) > 0 THEN TRUNC((dbms_lob.getlength(A.PHOTO)/2000) + 1)
            ELSE TRUNC(dbms_lob.getlength(A.PHOTO)/2000)
        END INTERATION_COUNT,
        a.PHOTO as FILE_CONTENT

      FROM employee_photo A WHERE A.employee_no = '123456'
)
,OFFSETS AS
(
    SELECT
        (2000 * (ROWNUM-1)) + 1 AS OFFSET,
        I.MOD,
        I.FILE_CONTENT_LENGTH,
        I.INTERATION_COUNT,
        i.FILE_CONTENT
    FROM INFO I
     CONNECT BY LEVEL <= I.INTERATION_COUNT
)
,RESULT AS
(
    SELECT
        DBMS_LOB.SUBSTR(O.FILE_CONTENT, 2000, O.OFFSET) AS CONTENT,
        O.OFFSET,
        O.MOD,
        O.FILE_CONTENT_LENGTH,

        O.INTERATION_COUNT
    FROM OFFSETS O
)
SELECT * FROM RESULT R ORDER BY R.OFFSET ASC

查询结果会把BLOB字段拆分为多行，每行2000个字节，程序按字段 OFFSET 顺序拼接起来即可