Why am I getting the An expression of non-boolean type specified in a context where a condition is expected, near ',' error

Question

This is my code:

SELECT * 
FROM mytable 
WHERE (Permit,Stampdate) IN (SELECT Permit,MAX(Stampdate) AS Stampdate 
                             FROM mytable GROUP BY Permit)

Answer 1

SQL SERVER doesn't support this.

You have to switch to a subwquery

CREATE TABLE mytable (Permit integer,Stampdate Datetime)
GO

INSERT INTO mytable (Permit,Stampdate) VALUES (1,GETDATE()),
 (1,DATEADD(day, DATEDIFF(day, 0, GETDATE()), '05:30:00'))
GO

SELECT * 
FROM mytable As t1
WHERE 
  EXISTS ( SELECT 1 FROM
( SELECT Permit,MAX(Stampdate) AS Stampdate

    FROM mytable As t2
       GROUP BY Permit) t2 WHERE  t1.Permit = t2.Permit 
      AND t1.Stampdate = t2.Stampdate
)
GO

Permit | Stampdate              
-----: | :----------------------
     1 | 2020-07-02 16:22:06.897

SELECT * 
FROM mytable As table1
GO

Permit | Stampdate              
-----: | :----------------------
     1 | 2020-07-02 16:22:06.897
     1 | 2020-07-02 05:30:00.000

    SELECT Permit,MAX(Stampdate) AS Stampdate  
    FROM mytable As t2
GROUP BY Permit
GO

Permit | Stampdate              
-----: | :----------------------
     1 | 2020-07-02 16:22:06.897

db<>fiddle here