Question

sql怎么统计某一课程的各分数段的人数？（在php程序里）

$cid = $_GET['id']; 课程id是cid用get方法传来了，cid和学生成绩 sgrade都在在grade表里，求代码

Answer 1

实现上面sql查询结果的记录总数
$sql = select count(C.`cid`) as `c` from (select * from `ctable` group by pid) as C left join `ptable` as P on P.`pid` = C.`pid`;
详解，此语句用到了sql子查询,先使用子查询对ctable进行分组查询，然后对分组后的结果集进行统计.

追问

这样写就可以了么？能详细点么？总是出现unexpexted ‘count’的错误

Answer 2

select count(*) from grade where cid = $cid group by sgrade;
你分数段是什么意思,是指60-80多少人,80-100多少人? 还是 61分 2人 ,62分0人 , 63分3人.....这样?

追问

每十分分一段啊

追答

select

sum(case when sgrade 89 then 1 else 0 end) as 'scroeA',
sum(case when sgrade 79 then 1 else 0 end) as 'scroeB',
sum(case when sgrade 69 then 1 else 0 end) as 'scroeC',
sum(case when sgrade 59 then 1 else 0 end) as 'scroeD'
from grade where cid = $cid group by sgrade;

追问

Parse error: syntax error, unexpected 'sum' 用count时也是这个错误

Answer 3

select max(kcfs) from table grop by 分数段

Answer 4

select count(*),sgrade from grade where cid={$cid} group by sgrade

追问

Parse error: syntax error, unexpected 'count'
我试了很多次，count老是出错

追答

擦，不至于吧，这是语法错误诶，你是不是哪些标记或标点符号错了