EntityFramework查詢oracle數據庫時報ora-12704: character set mismatch

1、這段linq，執行期間報ora-12704:character set mismatch錯誤。

var query = from m in ctx.MENU
    where (m.SUPER_MENU_ID ?? "") == (parentMenuId ?? "")
    orderby m.SORT_ID descending
    select new { m.SORT_ID };

生成出來的sql如下：

SELECT "Project1"."SORT_ID" AS "SORT_ID"
   FROM (

SELECT "Extent1"."SORT_ID" AS "SORT_ID"
   FROM "BA"."MENU" "Extent1"
 WHERE ((CASE WHEN("Extent1"."SUPER_MENU_ID" IS NULL) THEN '' 
                    ELSE "Extent1"."SUPER_MENU_ID" END) =
        (CASE WHEN(&p__linq__0 IS NULL) THEN '' 
                    ELSE &p__linq__0 END))

) "Project1"
ORDER BY "Project1"."SORT_ID" DESC

但是這條sql單獨放到plsql里跑是OK的。

 

2、改成這樣，讓生成的sql去掉了里面的case when就OK了。

parentMenuId = parentMenuId ?? "";
var query = from m in ctx.MENU
      where m.SUPER_MENU_ID == parentMenuId
    orderby m.SORT_ID descending
      select new { m.SORT_ID };

生成的sql如下：

SELECT "Project1"."SORT_ID" AS "SORT_ID" FROM ( 

SELECT "Extent1"."SORT_ID" AS "SORT_ID"
   FROM "BA"."MENU" "Extent1"
WHERE ("Extent1"."SUPER_MENU_ID" = :p__linq__0)

) "Project1"
ORDER BY "Project1"."SORT_ID" DESC

 

3、目前的猜測是，ef生成出來的case when有問題，調整linq不生成case when即可。但奇怪的是，同樣的sql在plsql里跑居然也是ok的，手工修改客戶端的字符集也無法在plsql里重現這個問題，如下：

修改注冊表里，HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_OraClient11g_home2\NLS_LANG，在plsql里客戶端使用不同於服務端的字符集，但無法生成同樣的錯誤。

修改前：

NLS_LANG = SIMPLIFIED CHINESE_CHINA.ZHS16GBK
Character Sets
Character size: 2 byte(s)
CharSetID: 852
NCharSetID: 2000
Unicode Support: True
NLS_LANG: SIMPLIFIED CHINESE_CHINA.ZHS16GBK
NLS_CHARACTERSET: ZHS16GBK
NLS_NCHAR_CHARACTERSET: AL16UTF16

修改后：

NLS_LANG = SIMPLIFIED CHINESE_CHINA.AL32UTF8
Character Sets
Character size: 2 byte(s)
CharSetID: 873
NCharSetID: 2000
Unicode Support: True
NLS_LANG: SIMPLIFIED CHINESE_CHINA.AL32UTF8
NLS_CHARACTERSET: ZHS16GBK
NLS_NCHAR_CHARACTERSET: AL16UTF16

 

4、updated on 2014.06.03，問題有了新的線索，下面這條linq仍然會報同樣的錯誤：

R1 == null ? string.Empty : R1.Emp_ID

但把string.Empty改成""就OK，很怪：

R1 == null ? "" : R1.Emp_ID

 

5、這個問題只是暫時解決，仍然存疑中，待完善。主要參考這篇：

《ef4 part 8: database agnostic linq to entities》