如何在内连接中添加大小写

Question

甲骨文:在内连接中，我想检查条件-1，如果条件A是成功，条件2，如果条件b成功。为此，我写了下面的，但没有运气。

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

Answer 1

CASE表达式必须返回如下所示的值：

INNER JOIN student_unit_attempt sua 
on sua.person_id=sei.person_id 
AND sua.course_cd=sei.course_cd 
AND sua.unit_attempt_status = CASE 
  WHEN i_unit_attempt_status IS NOT NULL THEN 'ENROLLED' 
  ELSE 'COMPLETED' 
END

将CASE返回的值与sua.unit_attempt_status进行比较。

Answer 2

尝试将WHERE子句中的逻辑重新定义为甚至不使用CASE

SELECT ...
INNER JOIN student_unit_attempt sua
    ON sua.person_id = sei.person_id AND
       sua.course_cd = sei.course_cd AND (
       (i_unit_attempt_status IS NOT NULL AND sua.unit_attempt_status = 'ENROLLED') OR
       (i_unit_attempt_status IS NULL AND sua.unit_attempt_status = 'COMPLETED'));