DROP DATABASE IF EXISTS mcs188_db;
CREATE DATABASE mcs188_db;
USE mcs188_db;
CREATE TABLE t1 (a INT, b CHAR(5))ENGINE=Columnstore;
INSERT INTO t1 VALUES (NULL, NULL),(1, 'aaa'),(2, 'aaa'),(1, 'ccc'),(4, 'ddd'),(5, 'aaa'),(6, 'ddd'),(7, 'eee');
SELECT AVG(DISTINCT a) FROM t1;
AVG(DISTINCT a)
4.1667
SELECT AVG(DISTINCT a) FROM t1 GROUP BY b HAVING b = 'aaa';
AVG(DISTINCT a)
2.6667
SELECT b, AVG(DISTINCT a) FROM t1 GROUP BY b ORDER BY b DESC;
b	AVG(DISTINCT a)
eee	7.0000
ddd	5.0000
ccc	1.0000
aaa	2.6667
NULL	NULL
SELECT AVG(a) FROM t1;
AVG(a)
3.7143
DROP DATABASE mcs188_db;