有人能帮我一下吗
内部连接student_unit_attempt sua on sua.person_id=sei.person_id和sua.course_cd=sei.course_cd,以及(当i_unit_attempt_status不为空时(sua.unit_attempt_status =‘sua.unit_attempt_status’),当i_unit_attempt_status为NULL时(sua.unit_attempt_status =‘已完成’)结束
[Password_Last_Changed] [datetime] ASWHEN ([SUA_History1_Date] IS NOT NULL) then [SUA_History1_Date]WHEN ([SUA_History2_Date] IS NULL)then [SUA_History3_Date]
WHEN ([S