同时选择字段的最小日期和最大日期

Question

I have this query which returns the min date value respective to the field.

SELECT sa.ContentID, SA.MSISDN, sa.DateRegistered AS minDate, sa.DateRegistered AS maxDate 
FROM sms.dbo.SubscriptionsArchive AS sa 
INNER JOIN (SELECT MSISDN, MIN(DateRegistered) AS mindate 
            FROM sms.dbo.SubscriptionsArchive 
            GROUP BY MSISDN) mysa 
ON sa.MSISDN = mysa.MSISDN AND sa.DateRegistered = mysa.mindate 

It's output is

But I want to display the max date value for the same date as well in addition to min date. How do i achieve that?

Answer 1

Although it may be tempting to use a second subquery join to get the MAX() , and again join it by MSISDN an the max date, you should be able to achieve it by adding the MAX(DateRegistered) into the existing subquery and adding an OR condition in the join's ON clause to join either on the MSISDN,mindate or on MSISDN,maxdate .

SELECT
  sa.ContentID,
  SA.MSISDN,
  -- Use the join's dates by alias in the SELECT
  mysa.mindate,
  mysa.maxdate
FROM
  sms.dbo.SubscriptionsArchive AS sa 
  INNER JOIN (
    SELECT
      MSISDN,
      MIN(DateRegistered) AS mindate,
      -- Add the max date
      MAX(DateRegistered) AS maxdate,
    FROM sms.dbo.SubscriptionsArchive 
    GROUP BY MSISDN
  ) mysa 
    -- Join on either a mindate or maxdate match
    ON (sa.MSISDN = mysa.MSISDN AND sa.DateRegistered = mysa.mindate)
      OR (sa.MSISDN = mysa.MSISDN AND sa.DateRegistered = mysa.maxdate)

I notice that you tagged this as mysql but the dbo really suggests you are using MS SQL Server. If that is true, then you can use a common table expression rather than the subquery join.

-- Define the subquery as a CTE instead
WITH mysa AS (
 SELECT
    MSISDN,
    MIN(DateRegistered) AS mindate,
    -- Add the max date
    MAX(DateRegistered) AS maxdate,
  FROM sms.dbo.SubscriptionsArchive 
  GROUP BY MSISDN
);

SELECT
  sa.ContentID,
  SA.MSISDN,
  -- Use the join's dates by alias in the SELECT
  mysa.mindate,
  mysa.maxdate
FROM sms.dbo.SubscriptionsArchive AS sa
-- Join on the CTE
INNER JOIN mysa
  ON (sa.MSISDN = mysa.MSISDN AND sa.DateRegistered = mysa.mindate)
  OR (sa.MSISDN = mysa.MSISDN AND sa.DateRegistered = mysa.maxdate)

Answer 2

Your syntax suggests SQL Server. If so, I would suggest window functions:

SELECT sa.ContentID, SA.MSISDN, sa.DateRegistered AS minDate, sa.DateRegistered AS maxDate 
FROM (SELECT sa.*,
             MIN(DateRegistered) OVER (PARITION BY sa.MSISDN) as mindr,
             MAX(DateRegistered) OVER (PARITION BY sa.MSISDN) as maxdr
      FROM sms.dbo.SubscriptionsArchive sa 
     ) sa
WHERE sa.DateRegistered IN (mindr, maxdr);