.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
(SELECTdbms_lob.getlength(A.PHOTO) AS FILE_CONTENT_LENGTH, MOD(dbms_lob.getlength(A.PHOTO),2000) AS MOD,CASEWHEN 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_CONTENTFROM 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_CONTENTFROM INFO ICONNECT BY LEVEL <= I.INTERATION_COUNT
)
,RESULT AS
(SELECTDBMS_LOB.SUBSTR(O.FILE_CONTENT, 2000, O.OFFSET) AS CONTENT,O.OFFSET,O.MOD,O.FILE_CONTENT_LENGTH,O.INTERATION_COUNTFROM 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