SQL Server 2017

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CREATE TABLE tablename ([Column1] varchar(1), [Column2] int);
    
INSERT INTO tablename ([Column1], [Column2]) VALUES
    ('A', 200),
    ('A', 200),
    ('A', 0),
    ('B', 300),
    ('B', 200),
    ('C', 100);
6 rows affected

SELECT DISTINCT Column1,
       AVG(CASE WHEN Column2 <> 0 THEN Column2 END) OVER (PARTITION BY Column1) Column2
FROM tablename;


Column1
Column2


A
200

B
250

C
100


Warning: Null value is eliminated by an aggregate or other SET operation.


SELECT DISTINCT Column1,
       AVG(Column2) OVER (PARTITION BY Column1) Column2
FROM tablename
WHERE Column2 <> 0;


Column1
Column2


A
200

B
250

C
100


SELECT DISTINCT Column1,
       AVG(CASE WHEN Column2 <> 0 THEN 1.0 * Column2 END) OVER (PARTITION BY Column1) Column2
FROM tablename;


Column1
Column2


A
200.000000

B
250.000000

C
100.000000


Warning: Null value is eliminated by an aggregate or other SET operation.


SELECT DISTINCT Column1,
       AVG(1.0 * Column2) OVER (PARTITION BY Column1) Column2
FROM tablename
WHERE Column2 <> 0;


Column1
Column2


A
200.000000

B
250.000000

C
100.000000