ORACLE小问题但很急，希望高手来帮解决一下
UPDATE T1_PSN_HR
 SET UNIT_XT=(SELECT DISTINCT B.ID FROM T1_PSN_HR A,T2_ORG_TRAN B
  WHERE A.Org_Code_L2=B.HR_ORG_ID)

报的错误是UNIT_XT无效标识符，
我现在的情况是t1_psn_hr里边有这个 unit_xt字段且是varchar2型
而select 语名查出来的B.ID是varchar2型的
为什么update不进去，，谢谢做答

------解决方案--------------------

SQL code

UPDATE T1_PSN_HR A
   SET UNIT_XT = (SELECT MAX(B.ID)
                    FROM T2_ORG_TRAN B
                   WHERE A.ORG_CODE_L2 = B.HR_ORG_ID)
 WHERE EXISTS
 (SELECT 1 FROM T2_ORG_TRAN B WHERE A.ORG_CODE_L2 = B.HR_ORG_ID);