rows number unexpectedly change after changing COUNT(DISTINCT) to COUNT

// Some comments here

MariaDB [test]> SELECT t2.c10 AS c10, COUNT(t2.c15) AS col_1 FROM t2 AS t2  GROUP BY t2.c6, t2.c10 HAVING (MAX(t2.c11) <= 1);

+--------+-------+

| c10    | col_1 |

+--------+-------+

| value2 |     1 |

+--------+-------+

1 row in set (0.00 sec)

MariaDB [test]> SELECT t2.c10 AS c10, COUNT(DISTINCT t2.c15) AS col_1 FROM t2 AS t2  GROUP BY t2.c6, t2.c10 HAVING (MAX(t2.c11) <= 1);

+--------+-------+

| c10    | col_1 |

+--------+-------+

| value3 |     1 |

| value2 |     1 |

| value1 |     1 |

| value1 |     1 |

| value2 |     1 |

+--------+-------+

5 rows in set (0.00 sec)

DROP DATABASE IF EXISTS test;

CREATE DATABASE IF NOT EXISTS test;

USE test;

CREATE TABLE t2 (

    c1 INT NOT NULL AUTO_INCREMENT,

    c2 INT NOT NULL,

    c3 DECIMAL(10,2) NOT NULL,

    c4 VARCHAR(50) NOT NULL,

    c5 DATE NOT NULL,

    c6 MEDIUMTEXT NULL,

    c7 LONGTEXT NULL,

    c8 MEDIUMBLOB NULL,

    c9 LONGBLOB NULL,

    c10 ENUM('value1','value2','value3') NULL,

    c11 SET('a','b','c','d') NULL,

    c12 BIT(8) NULL,

    c13 DATETIME NULL,

    c14 FLOAT(8,2) NULL,

    c15 DOUBLE(12,4) NULL,

    PRIMARY KEY (c1)

);

INSERT INTO t2 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15) VALUES (994, 3423, 181.05, 'sample_wfxp8dzD7XrFnPLzr', '2024-12-16', 'sample_pVtuVRHgHyCTAdMjTX5uDmgDFTTcRtYK4MA3VzWGhxyRAthAan095ltHnWC2wZqFzmNIz2BhrrY2h0fxo8UzijtqT3Qzyc7ydCZ760AbwzyWxKRhxPNIiXBNmglw9ylwoKoF0Q5QMAuWKKHLT07TyALEjZEq9SXDPPHZkG637npBmt2TKOxONpcXFVVrsW3jgaSAVhmwZMYON8YAyhzkhs0fsDZAohNdcrXeb43HI5de5EWnnY2lj8xyjRyfvWyVnBrhfeRiVnwUHuk0bcwoN3ueyVTRnXwQSF56ZbxUsw4hUmzUQ4GGRNJqlHOzrdMFLZHnsp5SamGZ0WPFJC1Vx1RuAnB5RdThXSIL8o2Fgebw5VIlETIWBvsuSQqrlbUxl0DbKa4xwcIiP23T8cVxdUgU4xKNvx6nab1kO47gdMcGoSGyXyvr23yKaVpjtw6XNe0uwE6zNt4nqZ1IMHxo', 'sample_oIxWhZ5PNoCnBUDNNG1t4uGQ80Jm3dOMyFRe0xsG8bqvWYFDuMqCy715ukwGqx4YD0tNg95vNkY49I1JPAbh5BBrcbTCYpkH1R37hDwaEo0Lzl91rc0tCeXUzOy258wzk7DX3Z11LNDgWU4awzLAAqwgg6l6QUVNdWbDUN3MQYXgivI8FcfivR8MVM40OIkt9fO8BNRyM2wTSSdov5M69ahQHUactc9lQyhXQfKFssG6OK2qKe2LIxK7FT1nHxPTNh7d41fB2bHcrjQ51tWpKJcLUFVVansOZC4fsvYKAamSAEMg3CsdHRNxw9dNCn5504tI75YCiAZT9DJEv7eTX7R07OJUaKE95P4VCs4XzftyMlVR4sPXkCsh7k7MYYBRd5d9iJdQLLOKXV3FUX5qjMRwF0oltoDkNGhVzUwlRuOptO8ROwzJLwCo5Zc7ce9l3bVoWQ3LsFymuRfVPQNPDkec3GZtAddEZBmIvzojWCpi0vhTzdYojxEdQwMHomRvrrYI7XWkrLrOOYwgMnPfHTeyO9oBFhEksiqIvbJHAEP2xCD2J0NvGcap1lZc2ueOUe6pJbZ95HmiFyRwwxMOxfLY4VCD5vgXNZTzeP0q8G0caUPPmLnaPcrw0vcnvR1gJnPdl8YyggslnNMOFmhPU2TK8EO5Xn6QVpvb6zPaM3Bw6sK3u10cw3i3jPuAYGSdMFNIdrU6L0zMUiI1LO4T7us2MUaXM', X'4DD6A6D687C6A9C08CDA93E9B48429DAA8ECBF93E891B67DDEBCDEBCE79C8A20', X'CF8CCBA2C880ED9DA9CF8644ECA5BD53E6B0AAED898E10C398D0AD', 'value1', 'a,c,b,d', b'01101010', '2025-04-25 18:28:30', 90.91, 53.96);

INSERT INTO t2 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15) VALUES (9219, 8711, 166.61, 'sample_b7C1trecK6yntdY4x3tkM8epFQtYVnoEfz17wiJ0h80', '2025-04-12', 'sample_lM7ywI1JmA9kqk0PwSZZlxesXZdCBedJvwYKBw9dR56w7WO7DzbB1ZVsW2uBiEHEd2wR0zfA4sx55xrLO89GGMf4F2mz0UofYA4LoqJgyFeasOQ0xqixQuPntbtFFaU0qHyeuRqR7GpKm67SSQeJQd5eZ7q71APzN3n0zFxL9bC0jVQUAA2zi4LuWSd0Py4RHM12FEZBN1KuHU5ZozMhLHirnlRKFd0CHuHyUguieTnEjt89dxMMgaDrETZaKHVR1ScgTZefc8hb2Y5a2zsDfzRCQbzUBuZhyxWPDkLMg5eJaLJRAGHMN71OJrpgGZCWwFkmvr3GquST0vH8CnT59cLY9O9v9udhzAtGCiQXbwB5Lj7KzeYHgjKr8X09e6EGFI4JxrFhFkCd8iyB8xSq8NysRpDP91m9AphkU', 'sample_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', X'3E00CE8341C791EE918038EE949521C58A15D0B301D3BBE09EADEBBDA75BE890B0D58D53', X'37', 'value1', 'c,b,a', b'11010111', '2025-01-23 17:58:04', 97.71, 79.57);

INSERT INTO t2 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15) VALUES (2340, 3423, 789.64, 'sample_JtpdkPugJClf6wBGA48lgU0DFFQny1d', '2025-01-19', 'sample_7R6EMmsSUYkMz6YCdnJKFiZabj1AjoceqELoBIvttyuANntWJL2Iguil0ggBEhhicCIyajZZCbnYcoia8z8m2xhobdtGwkvfOFQCJYstbgEOwNRMKP3JikRrYTGn6M16dllazrq68Ih1EE6ZgTAYVDzjsMXfYMHELWNupyYn5JJzpScnf9xkHTtu4IoNR4WeVzHt1nzkrI8VhXULipuUH1s9gmSc8Pean8HlBr9tXw2vG5E0N04ZbCricxniIf4xVAEc7Q8n7hVRH58ZsdYOhX', 'sample_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', X'E4B6A42FC3B5E9B69AD0A3EB9DA6EF81A0', X'1CCFA9', 'value3', 'c,b', b'10001011', '2025-03-23 19:05:28', 76.33, 87.70);

INSERT INTO t2 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15) VALUES (4869, 3575, 142.83, 'sample_kvsDX71mAzReVmNhu7QiIsYUoE1SqxJ', '2025-10-06', 'sample_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', 'sample_yNZHZaFHLQgwQWXReALBSnzD7MedQ4MyNNoq2IkJcCBII1LsMJOxWnghWPoV7J6OioviMpRvYPhL5nVVL4lMipjQ8KMx1Nvb8lnAecdyZI4wjhOrsfTycULPar8lnvNq8LtqlQLIQ11yXh3m4iQmRQ02IE2j58K41wh5fyGhNz9TrpFSJhgNx2F4ur3QdqtXHwaWRUgUdIJoWoxmOO2VbaitXDUbHOuJQ5tIYOI5pGckmQ0Vvm5HcO63qGRVcI9dRsffTbVewbe8V9ILyVMVsGPLZtM6oSvbcJHmMHjQ5yeykw1xD4CXVPQ0akzZ5efk2xSWljsMPMMipqvWhxZ7bJAKQmEjJlqQxT2fpipbyZW9cQP8dPZJnENYgzbS95yIb6bfyM8W0rGKrfPQuouljwPS59KgjnKQnfoZhNtO1E1xPe545PknJFz54tjlBWrXqZddEJzhIDImuOxoCUA3ufUgW0yGWatfRF42ezcOZ86XAA5RBVGHyvcC81Co1T5HkOXKFt8ezOiJm9NJL2oglSgYmmWeGusXjGlfW2TZsZ3wIiihLAzhHakzBeNRzHkMDxhTZKpMh6ffzCbbx01w7Q39AJq56cARqTSVnezmruYNpbolbJW80TmA3HLre35IpFzwWXAnskRLK3pK0n2cS8Me1DOEdex8oOjt5xexovpSDTXjfP0n16NKfnN6mktohLiEaSQD4BX2TUPK1Hq27ilJVvrgWGmMTBCMfJoIs8slcahobaEaHenTQf8z7fFIOKSxf7Y5KGKGxRMYZ0eFzWqH93Vmxy0HQqZdrn3HrDp1FzeL6B7Fs414VEVG6MmXTE406DM4LprcOaIBfWZjrZfix3MtWhrTH01GQfjDEXnrmDNoS3d6CjLcfrXDFtUGVkq0JZgnGwt1xMimL5kLHwkdJstZfinf7u97PoFqQfLWpJB0YymynZqiMfzUW8Ob7JWu4KbbsnVz6G4qUsYgYSY4wxPKFfXH7ZfNamHiH4z3AQpGQzEX5ndr1ZwNNDKQzmGKbajKJ5UFeGqNwkytRDIMQdf1f6GxRUYtKYGXvrB1a0U3atr2OuWQAw2LqTbEBVlLAaEg2h8uuqsCB5LfG8NCk3vnHjQhY7IuNx7NAEFByTHvowl8WYBhKfkxzaW3i7S9sepXb18okFtcmBC8nUMJjSU1f7fIsQMBgGJaa3w9Zrl8gVk9MtiJ8u8BjelfqaXb3kf6obkJOfTdXtscFpimU8vuzf7CZPq8dTbAkFzLGbIyNigXiKSK1fAzABEn9qowlSmWstEoOFrK8YfK3k17ZKdrnwBOaayXyS5xTOPZtUniNo2xA6Q9kRcLeQt5pPxqxKDsqYTj55Q6tJ4qAkcGx5fGnOKlekCaOCKBmmz2kXpdgw2Oj1nAKZDD2H5sf3Ft72qE0BtJgmmrONar7PQSVJoDXiTG1IhN3n5OdW9XzV3V19Wr5dGg6wiOiVCyfIBqBw0QOsiA72ytK061bEPeMZgVb0bIJ8baepvqsB9PSas5AkTii5hVyVPSyu3gbzxWeomK8v0mAru84wOw6gWCvtFwrtb2npkR4acPVBFSgSXOmkUjS16uuCRHlePnuXlU5Ui0ZBADCbF2UnVB1Hln6oeuIe7udCnV1NUb9dmiOpYQjpnBEntitZii9cdh5orHjYzX86R2SeailHTHKlsgsnItuzhPfsjGhYYp3NsNQStB', X'3D1AE4B784D7AC78', X'D5B3D18ED3B57BDEA87764DCAFCB84C5B8E3B88A46E09A8574CB9AE8B8BEEA87B1E4A8A4E9BF99CBA3D68DE896AA4C190F', 'value2', 'a', b'01000001', '2025-06-18 19:15:19', 8.76, 22.64);

INSERT INTO t2 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15) VALUES (1830, 3584, 983.64, 'sample_dPiBN3CgbQXn', '2025-01-31', 'sample_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', 'sample_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', X'2626', X'56E794A953CFAB30E39CA81DC98552E58B9D74C494E5979836EEA38EEE8C9305E895BCCFB465D49FC9BCC8B0', 'value2', 'b,d,a,c', b'00111000', '2024-12-04 05:24:10', 24.29, 84.91);

SELECT t2.c10 AS c10, COUNT(t2.c15) AS col_1 FROM t2 AS t2  GROUP BY t2.c6, t2.c10 HAVING (MAX(t2.c11) <= 1);

SELECT t2.c10 AS c10, COUNT(DISTINCT t2.c15) AS col_1 FROM t2 AS t2  GROUP BY t2.c6, t2.c10 HAVING (MAX(t2.c11) <= 1);