Question

我的数据库中有数据

ID    UserID   CourseName   Grade                                  
 1      8        CourseA      75
 2      8        CourseA      102 
 3      8        CourseA      115
 4      8        CourseA      111
 5      8        CourseA      112
 6      8        CourseB      60
 7      8        CourseB      45
 8      8        CourseB      58
 9      8        CourseB      60
 10     8        CourseB      74
 11     8        CourseC      130
 12     8        CourseC      140
 13     8        CourseC      133 
 14     8        CourseC      135

我需要上一个更新的成绩，如

`8     CourseA   112    
 8     CourseB   74
 8     CourseC   135`

有人可以建议我这样的SQL查询。

Answer 1

好的，更新我的回答：

知道了：

SELECT UserID, CourseName, Grade
FROM yourtable
WHERE UserID = '8'
AND ID
IN (
    SELECT MAX( ID ) 
    FROM yourtable
    GROUP BY CourseName
)

Answer 2

您可以添加其他列修改日期

alter table tableName add column modifiedDate DEFAULT NOW() ON UPDATE NOW()

然后您获得课程的最后更新成绩

 select * from tableName where course ='CourseA' 
 order by modifiedDate desc limit 1

Answer 3

select * from Course a 
where id=(select max(b.id) from Course b where b.CourseName=a.CourseName);

Aftwerwards您可以按ID，CourseName

对结果进行分组

未经测试！

Answer 4

SELECT * FROM Table ORDER BY ID DESC LIMIT 1;

Mysql查询最后更新的行

4 个答案: