DROP DATABASE IF EXISTS mcs115_db;
CREATE DATABASE mcs115_db;
USE mcs115_db;
CREATE TABLE t1 (a INT, b CHAR(1))ENGINE=Columnstore;
INSERT INTO t1 VALUES(NULL, ''),(1, 'z'),(2, 'y'),(1, 'y'),(2, 'z'),(3, 'z');
SELECT COUNT(a) FROM t1;
COUNT(a)
5
SELECT COUNT(DISTINCT a) FROM t1;
COUNT(DISTINCT a)
3
SELECT COUNT(DISTINCT b) FROM t1;
COUNT(DISTINCT b)
3
DROP DATABASE mcs115_db;