在MySQL中，我們可以使用子查詢來查找學生連續(xù)兩次不及格的情況。下面是一個簡單的例子：

SELECT s1.student_id, s1.course_id, s1.grade, s2.grade 
FROM scores s1, scores s2 
WHERE s1.student_id = s2.student_id 
AND s1.course_id = s2.course_id 
AND s1.grade < 60 AND s2.grade < 60 
AND s1.year = s2.year AND 
((s1.semester = s2.semester AND s1.week = s2.week-1) 
OR (s1.semester = s2.semester-1 AND s2.week = 52 
AND s1.week = 1))

這個查詢使用了兩個scores表的實例，它們都包含了學生的成績信息。我們通過s1表和s2表中的連接條件找到同一學生在同一課程中的成績信息。然后，我們使用WHERE語句過濾不及格成績，并且確保這些成績是連續(xù)的兩個學期。

如果你想查詢?nèi)＿B續(xù)兩次不及格的學生，可以這樣寫：

SELECT DISTINCT s1.student_id 
FROM scores s1, scores s2 
WHERE s1.student_id = s2.student_id 
AND s1.course_id = s2.course_id 
AND s1.grade < 60 AND s2.grade < 60 
AND s1.year = s2.year AND 
((s1.semester = s2.semester AND s1.week = s2.week-1) 
OR (s1.semester = s2.semester-1 AND s2.week = 52 
AND s1.week = 1))

在這個查詢中，我們只查詢學生學號，使用DISTINCT關鍵字去重復。