DROP DATABASE IF EXISTS mcs189_db;
CREATE DATABASE mcs189_db;
USE mcs189_db;
CREATE TABLE t1 (a INT, b CHAR(5))ENGINE=Columnstore;
INSERT INTO t1 VALUES (NULL, ''),(1, 'aaa'),(2, 'aaa'),(1, 'ccc'),(4, 'ddd'),(5, 'aaa'),(6, 'ddd'),(7, 'eee');
SELECT SUM(DISTINCT a) FROM t1;
SUM(DISTINCT a)
25
SELECT SUM(DISTINCT a) FROM t1 GROUP BY b HAVING b = 'aaa';
SUM(DISTINCT a)
8
SELECT b, SUM(DISTINCT a) FROM t1 GROUP BY b ORDER BY b DESC;
b	SUM(DISTINCT a)
eee	7
ddd	10
ccc	1
aaa	8
NULL	NULL
SELECT SUM(a) FROM t1;
SUM(a)
26
DROP DATABASE mcs189_db;