从 2 个表中获取结果的查询:
SELECT path.* FROM (SELECT tbc.course_name
slp.course_id,slp.student_type,slp.stu_reference_id,
count(slp.course_id) as counttotalWatchedStudents
from tbl_student_learning_path slp LEFT JOIN tbl_courses tbc
on tbc.course_pid = slp.course_id WHERE slp.stu_reference_id =34
and slp.student_type='institute' GROUP BY slp.course_id ) as path
查询结果表:
| course_id | totalCollegeStudents | fullwatchedStudentsCount | counttotalWatchedStudents | sumOfWatchPointsForWatchedStudents | totalStudentsAvg | fullwatchedAvg |
|-------------------------------|----------------------|--------------------------|---------------------------|------------------------------------|------------------|----------------|
| Number Systems | 9 | 0 | 3 | 60 | 20.0000 | 0 |
| Percentages | 9 | 0 | 3 | 30 | 10.0000 | 0 |
| Blood Relations | 9 | 3 | 3 | 300 | 100.0000 | 300 |
| Calandar | 9 | 3 | 3 | 300 | 100.0000 | 300 |
| Percentages | 9 | 3 | 3 | 300 | 100.0000 | 300 |
| Permutation & Combination | 9 | 3 | 3 | 300 | 100.0000 | 300 |
| Probability | 9 | 0 | 3 | 90 | 30.0000 | 0 |
| Ratios | 9 | 0 | 3 | 120 | 40.0000 | 0 |
| Time and Work | 9 | 0 | 3 | 150 | 50.0000 | 0 |
| Time Speed & Distance | 9 | 1 | 3 | 140 | 46.6667 | 100 |
| Averages | 9 | 3 | 3 | 300 | 100.0000 | 300 |
| Coding and Decoding | 9 | 3 | 3 | 300 | 100.0000 | 300 |
从上表中，我想在主查询中添加内部查询 查询应该是这样的:
( select count(t1.watched_percentage) from tbl_student_learning_path t1
WHERE t1.stu_reference_id =34 and t1.student_type='institute'
AND t1.watched_percentage >= 90 group by t1.course_id )
fullwatchedStudentsCount,
结果应该是这样的(这没什么，但是如果第一个表 counttotalWatchedStudents 的值为 3，则意味着有两种类型的人 1.学生观看满(watched_percentage>=90) 2.仍在观看的学生(watched_percentage 1-89) )
| fullwatchedStudentsCount | fullwatchedStudentsSum |
|--------------------------|------------------------|
| 2 | 200 |
| 1 | 100 |
| 0 | 0 |
| 2 | 200 |
| 1 | 100 |
| 1 | 100 |
| 0 | 0 |
| 2 | 200 |
| 2 | 200 |
| 1 | 100 |
| 2 | 200 |
| 1 | 100 |
最佳答案
如果我没理解错的话，你想把看到90%以上的学生汇总到另一列:
我会这样做:
SELECT tbc.course_name,
slp.course_id,
slp.student_type,
slp.stu_reference_id,
count(slp.course_id) AS counttotalWatchedStudents,
sum(if(slp.watched_percentage>=90, 1, 0)) AS fullwatchedStudentsCount
sum(if(slp.watched_percentage>=90, watched_percentage, 0)) AS fullwatchedStudentsSum
FROM tbl_student_learning_path slp
LEFT JOIN tbl_courses tbc ON tbc.course_pid = slp.course_id
WHERE slp.stu_reference_id =34
AND slp.student_type='institute'
GROUP BY slp.course_id
enter code here
希望对你有帮助
关于mysql - 从同一张表中获取记录数时如何编写mysql innerquery，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44022776/