如何选择所有行都具有的行ID

Question

There is a table:

+-------------+----------+
|stud_group_id|subject_id|
+-------------+----------+
|    1g       |   1s     |
+-------------+----------+
|    1g       |   2s     |
+-------------+----------+
|    1g       |   3s     |
+-------------+----------+
|    2g       |   1s     |
+-------------+----------+
|    2g       |   2s     |
+-------------+----------+
|    3g       |   1s     |
+-------------+----------+
|    3g       |   2s     |
+-------------+----------+
|    3g       |   4s     |
+-------------+----------+

I need to select subject_id learned by all stud_group_id . I expect

+----------+
|subject_id|
+----------+
|   1s     |
+----------+
|   2s     |
+----------+

How can I do this? Thanks

Answer 1

Try this one:

select 
    subject_id,
    count(distinct stud_group_id) as cnt
from
    <your_table>
group by
    subject_id
having cnt=(select count(distinct stud_group_id) from <your table>)

Answer 2

Something along the lines:

select count(stud_group_id) as num_learners_from_group, subject_id 
    from your_table group by subject_id 
    having num_learners_from_group = 
      (select count(*) 
         from stud_groups_table 
         where stud_groups_table.stud_group_id = your_table.stud_group_id
         group by stud_groups_table.stud_group_id)

Answer 3

You can use having clause as below :

select subject_id         
  from tab
 group by subject_id
having count(distinct stud_group_id) = ( select count(distinct stud_group_id) from tab )

Demo

Answer 4

您尚未提及表名，因此使用TABLE_NAME作为占位符。

select distinct subject_id from TABLE_NAME group by stud_group_id, subject_id

Answer 5

Hope this works for you:

select subject_id
from mytable
group by subject_id
having count(*) = (select count(distinct stud_group_id) from mytable)