查询获取同表中customerID列的每个唯一值的表的最大主键ID

Question

I'm trying to run a query that takes obtains the maximum QuestionnaireId value for each unique value in column VendorId.

So for example from this table:

QuestionnaireId  VendorId
1                10003
2                10004
3                10004
4                10006
5                10005
6                10007
7                10005
8                10005

I would obtain:

QuestionnaireId  VendorId
1                10003
3                10004
8                10005
4                10006
6                10007

I'm using the following code to get the maximum QuestionnaireId, but need another statement alongside it to get the unique VendorIds as well. Note that the statement I've included is just last segment of a large Join function to combine all of my tables into one.

WHERE Questionnaire.QuestionnaireId = (SELECT MAX(Questionnaire.QuestionnaireId) FROM Questionnaire)

Answer 1

Just use aggregation:

select max(q.QuestionnaireId) as QuestionnaireId, VendorId
from Questionnaire
group by VendorId;