In multi-table join/derived table scenarios, the return type length of `TRIM(ORD(c0))` is incorrectly deduced, causing the trailing character of the result string to be truncated (`14857150` becomes `1485715`).

1. 1. 1. Problem Description
         When a query involves multi-table joins, derived tables, temporary tables, and sorting, the result of `TRIM(ORD(c0))` is truncated to an incorrect maximum length during materialization/sorting. In a single-table query, constant folding via the primary key evaluates the expression early and produces the correct result. In a multi-table query, the expression is evaluated at runtime, and the optimizer deduces its return type length as `VARCHAR(7)` or similar, while the actual generated string length is 8, resulting in the trailing `'0'` being truncated.

1. 1. 1. How to Reproduce
         Execute the following SQL:

```sql
DROP DATABASE IF EXISTS repro_mariadb806_db1_min6;
CREATE DATABASE repro_mariadb806_db1_min6
CHARACTER SET utf8mb4 COLLATE utf8mb4_uca1400_ai_ci;
USE repro_mariadb806_db1_min6;

CREATE TABLE t4 (
c0 VARCHAR(100) NOT NULL,
PRIMARY KEY (c0)
) ENGINE=InnoDB
DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;

INSERT INTO t4 VALUES ('⳾v*');

CREATE TABLE vp_mariadb_database1_937_source LIKE t4;
ALTER TABLE vp_mariadb_database1_937_source
ADD COLUMN vp_rowid BIGINT NOT NULL FIRST;
ALTER TABLE vp_mariadb_database1_937_source ENGINE=InnoDB;

INSERT INTO vp_mariadb_database1_937_source (vp_rowid, c0)
SELECT ROW_NUMBER() OVER (ORDER BY c0), c0
FROM t4;

CREATE TABLE vp_mariadb_database1_937_left (
vp_rowid BIGINT NOT NULL,
c0 VARCHAR(100)
CHARACTER SET utf8mb4 COLLATE utf8mb4_uca1400_ai_ci
) ENGINE=InnoDB;

CREATE TABLE vp_mariadb_database1_937_right (
vp_rowid BIGINT NOT NULL
) ENGINE=InnoDB;

INSERT INTO vp_mariadb_database1_937_left
SELECT vp_rowid, c0 FROM vp_mariadb_database1_937_source;

INSERT INTO vp_mariadb_database1_937_right
SELECT vp_rowid FROM vp_mariadb_database1_937_source;

SET NAMES utf8mb4 COLLATE utf8mb4_uca1400_ai_ci;

– Single-table query
SELECT *
FROM (
SELECT TRIM(ORD(c0)) AS vp_ast_col_0,
-1914373596 AS vp_ast_col_1,
c0 AS vp_ast_col_2,
c0 AS vp_ast_col_3,
'' AS vp_ast_col_4
FROM vp_mariadb_database1_937_source
) q
WHERE q.vp_ast_col_2 = '⳾v*'
ORDER BY 1, 2, 3, 4, 5;

– Multi-table rewritten query
SELECT *
FROM (
SELECT TRIM(ORD(c0)) AS vp_ast_col_0,
-1914373596 AS vp_ast_col_1,
c0 AS vp_ast_col_2,
c0 AS vp_ast_col_3,
'' AS vp_ast_col_4
FROM (
SELECT l.vp_rowid, l.c0
FROM vp_mariadb_database1_937_left l
JOIN (
SELECT vp_rowid, CONCAT('vp:', vp_rowid) AS payload
FROM vp_mariadb_database1_937_right
) p ON p.payload = CONCAT('vp:', l.vp_rowid)
JOIN vp_mariadb_database1_937_right r
ON r.vp_rowid = p.vp_rowid
) vp_rel
) q
WHERE q.vp_ast_col_2 = '⳾v*'
ORDER BY 1, 2, 3, 4, 5;
```

1. 1. 1. Expected Behavior
         Both queries should return identical results, with `vp_ast_col_0` equal to `14857150`.

1. 1. 1. Actual Behavior
         In the multi-table query, `vp_ast_col_0` loses the trailing `'0'`.

1. 1. 1. Execution Plan Comparison
         *Single-table query execution plan:*
         ```
         1 | SIMPLE | vp_mariadb_database1_937_source

         const

         PRIMARY

         PRIMARY

         402

         const

         1

         ```
         Because `c0` is the primary key, `WHERE c0 = '⳾v*'` directly hits the primary key. The optimizer treats the entire row as a constant, and the outer `TRIM(ORD(c0))` is evaluated via constant folding, yielding the correct result `14857150`.

*Multi-table query execution plan:*
```
1 | SIMPLE | l

1 | SIMPLE | vp_mariadb_database1_937_right

1 | SIMPLE | r