after changing AVG(x) to AVG(-x) ,the value unexpectedly change

mysql> WITH cte_108 AS (SELECT (SELECT AVG(15) AS subq_col) AS col_2 FROM t2 AS apd42) SELECT REPEAT(subq.group_concat_399, 4) AS col_1 FROM (SELECT GROUP_CONCAT(s975.col_2 ORDER BY s975.col_2 SEPARATOR ',') AS group_concat_399, s975.col_2 AS col_2 FROM cte_108 AS s975 GROUP BY s975.col_2) AS subq;

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

| col_1                                                                                                                      |

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

| 0x31352E303030302C31352E3030303031352E303030302C31352E3030303031352E303030302C31352E3030303031352E303030302C31352E30303030 |

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

1 row in set (0.00 sec)

mysql> WITH cte_108 AS (SELECT (SELECT -AVG(-15) AS subq_col) AS col_2 FROM t2 AS apd42) SELECT REPEAT(subq.group_concat_399, 4) AS col_1 FROM (SELECT GROUP_CONCAT(s975.col_2 ORDER BY s975.col_2 SEPARATOR ',') AS group_concat_399, s975.col_2 AS col_2 FROM cte_108 AS s975 GROUP BY s975.col_2) AS subq;

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

| col_1                                                        |

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

| 15.0000,15.000015.0000,15.000015.0000,15.000015.0000,15.0000 |

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

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 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,

    c16 JSON NULL,

    PRIMARY KEY (c1)

);

INSERT INTO t2 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15, c16) VALUES (5217, 498, 835.13, 'sample_fNfG', '2025-06-14', 'sample_fmk5nNJEcTlHvPeK898aRIeFPiKwTlhiLdzE', 'sample_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', X'2EE6AA8B771A30', X'E889B1C38468C291', 'value2', 'd,c,b,a', b'10100010', '2025-03-09 17:59:43', 76.40, 8.99, '{"k1": 758, "k2": "mixed_41", "k3": ["tag_83"], "k4": {"k5": "B", "k6": [87, 5], "k7": {"k8": "user_61", "k9": "2026-01-22T17:38:11.813764"}}, "k10": true}');

INSERT INTO t2 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15, c16) VALUES (4536, 3166, 295.80, 'sample_T4qoLyIdjt', '2025-10-16', 'sample_nhDJm1PegFV7EZ7ClCSNKbL4AgR3mYtKSyGoCbj03banVB4aJqsOGxvONffylOqSHn5CPsMdOr066Zec79PF8znXF9oCuSiLMswxxcYAVFkBmQFctPCFYMBFH6wxActYblnu8pKWhy2rU67NJLneKaA6jRGRtdTAz7NOPr5o9qAymyPMVXJVetT4dAOjB5KanAaqsxz3TDOc0NvrkMsXQOy5mOypLI27xwfROUm2m5BAn0puHzpIUPa51pog5NsMuDg3V1CzEJFDVaK4o4n8eFnJkrgCv8osuh5WSpq04cpAZhbRsBhORHvJ6UnMta28pMchRa', 'sample_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', X'E88DAA30DD9172EDA2830F', X'E0ABBF', 'value1', 'd,a,b', b'01010100', '2025-02-21 14:25:46', 74.62, 32.73, '{"k1": 786, "k2": "sample_59", "k3": 363.02105002859486, "k4": true}');

WITH cte_108 AS (SELECT (SELECT AVG(15) AS subq_col) AS col_2 FROM t2 AS apd42) SELECT REPEAT(subq.group_concat_399, 4) AS col_1 FROM (SELECT GROUP_CONCAT(s975.col_2 ORDER BY s975.col_2 SEPARATOR ',') AS group_concat_399, s975.col_2 AS col_2 FROM cte_108 AS s975 GROUP BY s975.col_2) AS subq;

WITH cte_108 AS (SELECT (SELECT -AVG(-15) AS subq_col) AS col_2 FROM t2 AS apd42) SELECT REPEAT(subq.group_concat_399, 4) AS col_1 FROM (SELECT GROUP_CONCAT(s975.col_2 ORDER BY s975.col_2 SEPARATOR ',') AS group_concat_399, s975.col_2 AS col_2 FROM cte_108 AS s975 GROUP BY s975.col_2) AS subq;