首先我们新建一张测试表格,date_day为日期，score为成绩，表格名ceshi。

我们如果取近七天的每天总成绩数据，常用的sql应该是：

SELECT date_day,sum(score) as score FROM ceshi WHERE DATE_SUB(CURDATE(), INTERVAL 7 DAY) <= date(date_day) GROUP BY date_day ORDER BY date_day

执行结果为：

 这样虽然得出了结果，但是如果数据库里没有完整的7天数据，那么他只能得到已有的三天数据。

所以我们需要改一下sql，关联一张自己创建的7天日期临时表：

select d.date, IFNULL(T.score,0) socre from 
(
    SELECT CURDATE() AS date
    UNION ALL
    SELECT DATE_SUB(CURDATE(), INTERVAL 1 DAY) AS date
    UNION ALL
    SELECT DATE_SUB(CURDATE(), INTERVAL 2 DAY) AS date
    UNION ALL
    SELECT DATE_SUB(CURDATE(), INTERVAL 3 DAY) AS date
    UNION ALL
    SELECT DATE_SUB(CURDATE(), INTERVAL 4 DAY) AS date
    UNION ALL
    SELECT DATE_SUB(CURDATE(), INTERVAL 5 DAY) AS date
    UNION ALL
    SELECT DATE_SUB(CURDATE(), INTERVAL 6 DAY) AS date
)  d
left join(
    select date_day, sum(score) as score
    from ceshi
    group by DATE_FORMAT(date_day,'%Y-%m-%d')
) T on T.date_day = d.date
GROUP BY d.date

执行结果为 ：

 同理 如果我们想要得到本周7天的数据，那么只需要改下日期临时表格，

select d.date, IFNULL(T.score,0) socre from 
(
    select date_sub(curdate(),INTERVAL WEEKDAY(curdate()) + 0 DAY) as date
UNION ALL
select date_sub(curdate(),INTERVAL WEEKDAY(curdate()) - 1 DAY) as date
UNION ALL
select date_sub(curdate(),INTERVAL WEEKDAY(curdate()) - 2 DAY) as date
UNION ALL
select date_sub(curdate(),INTERVAL WEEKDAY(curdate()) - 3 DAY) as date
UNION ALL
select date_sub(curdate(),INTERVAL WEEKDAY(curdate()) - 4 DAY) as date
UNION ALL
select date_sub(curdate(),INTERVAL WEEKDAY(curdate()) - 5 DAY) as date
UNION ALL
select date_sub(curdate(),INTERVAL WEEKDAY(curdate()) - 6 DAY) as date
)  d
left join(
    select date_day, sum(score) as score
    from ceshi
    group by DATE_FORMAT(date_day,'%Y-%m-%d')
) T on T.date_day = d.date
GROUP BY d.date

执行结果为：