text: CREATE TABLE t
  (
      `d` Date,
      `s` LowCardinality(FixedString(3)),
      `c` UInt32
  )
  ENGINE = SummingMergeTree()
  PARTITION BY d
  ORDER BY (d, s);
  
  INSERT INTO t (d, s, c) VALUES ('2020-01-01', 'ABC', 1);
  INSERT INTO t (d, s, c) VALUES ('2020-01-01', 'ABC', 2);
  
  OPTIMIZE TABLE t;
  SELECT * FROM t;
  