如何一行項目複製到另一行

Question

我有如下表：

Student_ID Description 
1  0x 
2  0x1G800.... 
3  0x1F800.... 

student_id數據1具有空值，我怎樣才能在1使用SQL查詢複製student_id數據2的值。

Answer 1

這就是你要找的東西？

Update Student 
SET Description = (SELECT Description FROM Student WHERE Student_ID = 2) 
WHERE Student_ID = 1 

或使用JOIN：

UPDATE S 
SET S.Description = S2.Description 
FROM Student S JOIN 
    Student S2 ON S2.Student_ID = 2 
WHERE S.Student_Id = 1 

好運。