after changing SUM(dkx26.c2),the col_2's value unexpectedly change affected by UNION ALL

mysql> (SELECT SQRT(dkx26.c15) AS col_1, SUM(dkx26.c2) AS col_2 FROM t3 AS dkx26 WHERE (HOUR('2023-01-01 12:00:00') = 80) GROUP BY SQRT(dkx26.c15), dkx26.c11 ORDER BY dkx26.c11 DESC) UNION ALL SELECT SUM(14) AS col_1, MIN('2023-01-01 12:00:00') AS col_2;

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

| col_1 | col_2                                    |

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

|    14 | 0x323032332D30312D30312031323A30303A3030 |

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

1 row in set (0.00 sec)

mysql> (SELECT SQRT(dkx26.c15) AS col_1, -SUM(-dkx26.c2) AS col_2 FROM t3 AS dkx26 WHERE (HOUR('2023-01-01 12:00:00') = 80) GROUP BY SQRT(dkx26.c15), dkx26.c11 ORDER BY dkx26.c11 DESC) UNION ALL SELECT SUM(14) AS col_1, MIN('2023-01-01 12:00:00') AS col_2;

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

| col_1 | col_2               |

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

|    14 | 2023-01-01 12:00:00 |

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

1 row in set (0.00 sec)

DROP DATABASE IF EXISTS test;

CREATE DATABASE IF NOT EXISTS test;

SET GLOBAL sort_buffer_size = 64 * 1024 * 1024;

SET GLOBAL read_rnd_buffer_size = 8 * 1024 * 1024;

USE test;

CREATE TABLE t3 (

    c1 INT NOT NULL AUTO_INCREMENT,

    c2 INT NOT NULL,

    c3 INT NOT NULL,

    c4 YEAR NOT NULL,

    c5 DATETIME NULL,

    c6 TINYINT NULL,

    c7 SMALLINT NULL,

    c8 MEDIUMINT NULL,

    c9 BIGINT NULL,

    c10 LONGTEXT NULL,

    c11 GEOMETRY NULL,

    c12 TINYTEXT NULL,

    c13 TINYBLOB NULL,

    c14 SET('x','y','z') NULL,

    c15 TINYINT(1) NULL,

    PRIMARY KEY (c1)

);

INSERT INTO t3 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15) VALUES (9473, 3166, 7923, 2009, '2025-10-28 00:33:04', 64, 33, 23, 5, 'sample_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', ST_GeomFromText('POINT(-7.208789 -111.046928)'), 'sample_lo1SDGmMjznqDAbPH7lv1PLIycmmGnug3w9c1EMVaOOvVY0FM7GLWSZHVE6MVSrkzdR1XlrSer0Ae6U0ldCAgDDUG', X'CBBA34E99F8CDA95E4A2AFDF8210', 'z', NULL);

(SELECT SQRT(dkx26.c15) AS col_1, SUM(dkx26.c2) AS col_2 FROM t3 AS dkx26 WHERE (HOUR('2023-01-01 12:00:00') = 80) GROUP BY SQRT(dkx26.c15), dkx26.c11 ORDER BY dkx26.c11 DESC) UNION ALL SELECT SUM(14) AS col_1, MIN('2023-01-01 12:00:00') AS col_2;

(SELECT SQRT(dkx26.c15) AS col_1, -SUM(-dkx26.c2) AS col_2 FROM t3 AS dkx26 WHERE (HOUR('2023-01-01 12:00:00') = 80) GROUP BY SQRT(dkx26.c15), dkx26.c11 ORDER BY dkx26.c11 DESC) UNION ALL SELECT SUM(14) AS col_1, MIN('2023-01-01 12:00:00') AS col_2;