2

Code: MSSQL / Bigquery

SELECT EmployeeId, SessionLoginLocal, cast(MIN(SessionLoginLocal) as date)MinSession
FROM database.data_source.user_session_table 
Group by EmployeeId, SessionLoginLocal
Order by EmployeeId

Current output:

 Row | EmployeeId |  SessionLoginLocal  | MinSession
-----+------------+---------------------+------------    
   1 |        354 | 2017-12-12T07:29:36 | 2017-12-12     
   2 |        354 | 2017-12-11T16:58:21 | 2017-12-11     
   3 |        354 | 2017-12-12T10:59:34 | 2017-12-12     
   4 |        354 | 2017-12-11T18:32:59 | 2017-12-11     
   5 |        354 | 2017-12-11T18:33:34 | 2017-12-11     
   6 |        354 | 2017-12-11T17:16:58 | 2017-12-11     
   7 |        354 | 2017-12-12T10:56:29 | 2017-12-12     
   8 |        354 | 2017-12-11T19:37:54 | 2017-12-11     
   9 |        354 | 2017-12-12T10:57:52 | 2017-12-12

Desired Output

 Row | EmployeeId |  SessionLoginLocal  | MinSession
-----+------------+---------------------+------------    
   1 |        354 | 2017-12-12T07:29:36 | NULL   
   2 |        354 | 2017-12-11T16:58:21 | 2017-12-11     
   3 |        354 | 2017-12-12T10:59:34 | NULL   
   4 |        354 | 2017-12-11T18:32:59 | NULL   
   5 |        354 | 2017-12-11T18:33:34 | NULL   
   6 |        354 | 2017-12-11T17:16:58 | NULL   
   7 |        354 | 2017-12-12T10:56:29 | NULL   
   8 |        354 | 2017-12-11T19:37:54 | NULL   
   9 |        354 | 2017-12-12T10:57:52 | NULL

The goal of this view is to create a stacked column graph with the date along the X axis, and the number of sessions on the Y. Currently the number of sessions by distinct employee per day are displayed, now I am trying to include a second column with the minimum session date, basically highlighting when they had their first session. How do i create the column with the Min(SessionTime) to only include the first session and create nulls for their other sessions?

4

When you post questions like this, it's really helpful if you post your sample data as inserts, so anyone can hop in and immediately query it.

CREATE TABLE #whatever
(
    id INT,
    employeeid INT,
    sessionloginlocal DATETIME
);

INSERT #whatever ( id, employeeid, sessionloginlocal )
SELECT *
FROM (
VALUES 
(1,   354, '2017-12-12 07:29:36'),   
(2,   354, '2017-12-11 16:58:21'),   
(3,   354, '2017-12-12 10:59:34'),   
(4,   354, '2017-12-11 18:32:59'),   
(5,   354, '2017-12-11 18:33:34'),   
(6,   354, '2017-12-11 17:16:58'),   
(7,   354, '2017-12-12 10:56:29'),   
(8,   354, '2017-12-11 19:37:54'),   
(9,   354, '2017-12-12 10:57:52')
) AS x (id, employeeid, sessionloginlocal)

This code uses a case expression and MIN as a windowing function to find the min login time per user. When they match, we display it as a date. When they don't we display NULL.

SELECT *,
       CASE WHEN w.sessionloginlocal = 
               MIN(w.sessionloginlocal) OVER ( PARTITION BY w.employeeid ) 
               THEN CONVERT(DATE, w.sessionloginlocal)
               ELSE NULL
       END AS min_sessionlocal
FROM   #whatever AS w;

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