# `Fun_GetCh` (function)

> 获取字符串中数字


- **Type:** FUNCTION
- **Returns:** `varchar(100)`
- **Deterministic:** NO
- **SQL data access:** CONTAINS SQL

## Parameters

| # | Mode | Name | Type |
|---|---|---|---|
| 1 | IN | `str` | `varchar(100)` |

## Body

_Body is not pre-cached. To inspect: `mysql --defaults-file=~/.my.cnf -e 'SHOW CREATE FUNCTION `Fun_GetCh`'`._

## Narrative

**Business context:** String filter — header says `获取字符串中数字` ("extract digits from a string") but the body actually returns characters that do **not** match the regex `[u0391-uFFE5]` (the literal `u`-prefixed pattern is invalid; MySQL falls back to matching only the letter `u` and the ASCII range `0391`-`FFE5`, so the filter is effectively a no-op character whitelist). After stripping `-` and `+`, it accumulates the remaining characters.

**What it does:** strips `-` and `+`, then walks the string one char at a time appending each character whose REGEXP test against `'[u0391-uFFE5]'` is not 1. Effective behavior: returns the input with `-`/`+` removed. Header comment is inconsistent with the body.

**Invocation:** called from `Sp_Create_sControlFaceNameTable` and `Sp_Create_sControlFaceNameTableFive` (control/process-name table builders). With the regex broken, the filter step is a no-op — flag as bug suspect for maintainer audit.