如何显示具有对应的其他列最大值的唯一行

Question

I am trying to fetch max column value by grouping other column. I am almost near but stuck at last point. Here is me code

TABLE:

      id . sys_id        . renewal
      1  . aaad00101     . 0
      2  . aaad00101     . 1
      3  . aaad00104     . 0
      4  . aaad00102     . 0
      5  . aaad00101     . 2
      6  . aaad00103     . 0

SQL Query:

     "SELECT * FROM $company WHERE renewal IN (SELECT DISTINCT
      MAX(renewal)FROM $company GROUP BY sys_id) ORDER BY sys_id"

Result:

     aaad00101-0
     aaad00101-2
     aaad00102-0
     aaad00103-0
     aaad00404-0 

My code is showing max value with minimum value like top two results. But I want if max value is showing then it should not show minimum value in results.

Let me know what I am missing here. Thanks

Fixed It:

SQL Query:

   "SELECT * FROM $company WHERE id IN (SELECT DISTINCT MAX(id)FROM
    $company GROUP BY sys_id) ORDER BY sys_id";

Answer 1

Am I correct that you want to keep all the rows you currently have in your table with an additional column that shows the max renewal value for each sys_id?

It's something frequently done in a window function, but since MySQL doesn't currently have that capability you can get around it with an additional join.

SELECT a.*, b.last_renewal FROM company AS a JOIN ( SELECT sys_id, MAX( renewal ) AS last_renewal FROM company GROUP BY sys_id ) AS b USING ( sys_id ) ;

Or are you looking for a renewal value for the latest occurrence, which I assume is for the max value of the id column?

If that's the case, you can concatenate all of the renewal values into a list and order that list by id, and then you can take out the last value in that list.

SELECT sys_id, SUBSTRING_INDEX( GROUP_CONCAT( renewal ORDER BY id ),',',-1 ) AS last_renewal, MAX( id ) AS last_occurance FROM company GROUP BY sys_id ;