how to find out max of a field for two different conditions in sql

Question

I have a table EMPDATA with the following data:

EntityId    MeetDate    SourceCode  Status
1           06.11.2017   AB          FNL
1           05.2.2018    AB           


        

Answer 1

You can easily achieve the expected output using conditional aggregation:

SELECT EntityId,
       MAX(CASE 
              WHEN SourceCode = 'AB' AND status = 'FNL' THEN MeetDate 
           END) AS LastDate,
       MAX(CASE WHEN SourceCode = 'IU' THEN MeetDate END) AS InterimDate          
FROM mytable
GROUP BY EntityId

This query implements all logic described in the OP except for:

• InterimDate ... which has occurred after the latest Meetdate for SourceCode ‘AB’ and Status ‘FNL’.

You can implement this using a CTE so that the code looks cleaner:

;WITH CTE AS (
SELECT EntityId,
       MAX(CASE 
              WHEN SourceCode = 'AB' AND status = 'FNL' THEN MeetDate 
           END) AS LastDate,
       MAX(CASE WHEN SourceCode = 'IU' THEN MeetDate END) AS InterimDate          
FROM mytable
GROUP BY EntityId
)
SELECT LastDate, 
       CASE 
          WHEN InterimDate > LastDate THEN InterimDate
       END AS InterimDate
FROM CTE 

Demo here