使用where子句为不同的值选择id

Question

I have a table with columns: unique id, recipients, sent_date and status.

I would like select ids for distinct recipients when sent_date > xx and status = 'something'

I have tried this:

SELECT * 
FROM EmailMessage 
WHERE Recipients in
    (SELECT Recipients 
     FROM EmailMessage
     GROUP BY Recipients 
     HAVING COUNT(Recipients)=1)
and sent_date > '2018-12-31 23:59:59'
and status = 'failed'

But this produces too few results and something seems not right. I am using SQL Server MS.

Answer 1

I would like select ids for distinct recipients when sent_date > xx and status = 'something'

This translated in sql is this:

SELECT DISTINCT Recipients  
FROM EmailMessage 
WHERE 
  sent_date > '2018-12-31 23:59:59'
  AND 
  status = 'failed'

or

SELECT Recipients  
FROM EmailMessage 
WHERE 
  sent_date > '2018-12-31 23:59:59'
  AND 
  status = 'failed'
GROUP BY Recipients

Answer 2

This returns rows where the failure and date conditions are true:

SELECT em.*
FROM EmailMessage 
WHERE sent_date >= '2019-01-01' AND status = 'failed';

I'm not sure what "distinct recipient" means. But you can get one row per recipient using window functions (or some other method):

SELECT em.*
FROM (SELECT em.*,
             ROW_NUMBER() OVER (PARTITION BY recipient ORDER BY sent_date) as seqnum
      FROM EmailMessage 
      WHERE sent_date >= '2019-01-01' AND status = 'failed'
     ) em
WHERE seqnum = 1;