user_ID | User_name | semester | math | english |
1 | John | 1st | 67 | 73 |
1 | John | 2nd | 82 | 59 |
在此之后,我想将第一学期的学分与第二学期进行比较.即数学正在提高,英语水平正在下降
user_ID | User_name | math | english |
1 | John | good | bad |
我只是取结果但不知道如何解决.任何帮助将不胜感激
解决方法:
试试这个:
SELECT A.user_id, A.user_name, IF((B.math - A.math) > 0, 'good', 'bad') math,
IF((B.english - A.english) > 0, 'good', 'bad') english
FROM (SELECT user_id, user_name, math, english
FROM tbl_exam WHERE semester = '1st') AS A
INNER JOIN
(SELECT user_id, user_name, math, english
FROM tbl_exam WHERE semester = '2nd') AS B ON A.user_id = B.user_id