[doc](function) opt string function doc (apache#1849)

## Versions 

- [x] dev
- [x] 3.0
- [x] 2.1
- [ ] 2.0

## Languages

- [x] Chinese
- [x] English

## Docs Checklist

- [ ] Checked by AI
- [ ] Test Cases Built

---------

Co-authored-by: smallhibiscus <844981280>

docs/sql-manual/sql-functions/scalar-functions/string-functions/append-trailing-char-if-absent.md

@@ -24,37 +24,37 @@ specific language governing permissions and limitations
 under the License.
 -->
 
-## append_trailing_char_if_absent
+## Description
 
-### description
+Used to add a specific character (such as a space, a specific symbol, etc.) to the end of a string if the character does not exist at the end of the string. The function is to ensure that the string ends with a specific character.
 
-#### Syntax
+## Syntax
 
-`VARCHAR append_trailing_char_if_absent(VARCHAR str, VARCHAR trailing_char)`
+```sql
+APPEND_TRAILING_CHAR_IF_ABSENT ( <str> , <trailing_char> )
+```
 
-If the @str string is non-empty and does not contain the @trailing_char character at the end, it appends the @trailing_char character to the end.
-@trailing_char contains only one character, and it will return NULL if contains more than one character
+## Parameters
 
-### example
+| Parameters        | Description |
+|-------------------|-----------------------------|
+| `<str>`           | Target string to be judged |
+| `<trailing_char>` | Character to be added to the end of the string (if the character does not exist) |
 
-```
-MySQL [test]> select append_trailing_char_if_absent('a','c');
-+------------------------------------------+
-| append_trailing_char_if_absent('a', 'c') |
-+------------------------------------------+
-| ac                                       |
-+------------------------------------------+
-1 row in set (0.02 sec)
-
-MySQL [test]> select append_trailing_char_if_absent('ac','c');
-+-------------------------------------------+
-| append_trailing_char_if_absent('ac', 'c') |
-+-------------------------------------------+
-| ac                                        |
-+-------------------------------------------+
-1 row in set (0.00 sec)
-```
+## Return value
+
+Parameters The string after concatenation of `<str>` and `<trailing_char>` (if `<trailing_char>` does not exist in `<str>`)
 
-### keywords
+## Example
 
-    APPEND_TRAILING_CHAR_IF_ABSENT
+``` sql
+SELECT APPEND_TRAILING_CHAR_IF_ABSENT('a','c'),APPEND_TRAILING_CHAR_IF_ABSENT('ac', 'c'),APPEND_TRAILING_CHAR_IF_ABSENT('ac', 'cd')
+```
+
+```text 
++------------------------------------------+-------------------------------------------+--------------------------------------------+
+| append_trailing_char_if_absent('a', 'c') | append_trailing_char_if_absent('ac', 'c') | append_trailing_char_if_absent('ac', 'cd') |
++------------------------------------------+-------------------------------------------+--------------------------------------------+
+| ac                                       | ac                                        | accd                                       |
++------------------------------------------+-------------------------------------------+--------------------------------------------+
+```

docs/sql-manual/sql-functions/scalar-functions/string-functions/ascii.md

@@ -24,31 +24,36 @@ specific language governing permissions and limitations
 under the License.
 -->
 
-## ascii
-### Description
-#### Syntax
+## Description
 
-`INT AXES (WARCHAR STR)`
+Returns the ASCII code of the first character of a string
 
+## Syntax
 
-Returns the ASCII code corresponding to the first character of the string
+```sql
+ASCII ( <str> )
+```
 
-### example
+## Parameters
 
+| Parameter | Description |
+|-----------|-------------------------|
+| `<str>`   | The string whose ASCII code of the first character needs to be calculated |
+
+## Return value
+
+Parameter <str> ASCII code of the first character
+
+## Example
+
+```sql
+SELECT ASCII('1'),ASCII('234')
 ```
-mysql> select ascii('1');
-+------------+
-| ascii('1') |
-+------------+
-|         49 |
-+------------+
-
-mysql> select ascii('234');
-+--------------+
-| ascii('234') |
-+--------------+
-|           50 |
-+--------------+
-```
-### keywords
-    ASCII
+
+```text
++------------+--------------+
+| ascii('1') | ascii('234') |
++------------+--------------+
+|         49 |           50 |
++------------+--------------+
+```

docs/sql-manual/sql-functions/scalar-functions/string-functions/char-length.md

@@ -24,32 +24,42 @@ specific language governing permissions and limitations
 under the License.
 -->
 
-## char_length
-### Description
-#### Syntax
+## Description
 
-INT char_length(VARCHAR str)
+Calculates the length of a string. For multi-byte characters, returns the number of characters.
 
+Currently only supports `utf8` encoding
 
-Returns the length of the string, and the number of characters returned for multi-byte characters. For example, five two-byte width words return a length of 5, only utf8 encoding is support at the current version. `character_length` is the alias for this function.
+## Alias
 
-### example
+- CHARACTER_LENGTH
 
+## Syntax
 
+```sql
+CHAR_LENGTH ( <str> )
 ```
-mysql> select char_length("abc");
-+--------------------+
-| char_length('abc') |
-+--------------------+
-|                  3 |
-+--------------------+
-
-mysql> select char_length("中国");
-+------------------- ---+
-| char_length('中国')   |
-+-----------------------+
-|                     2 |
-+-----------------------+
+
+## Parameters
+
+| Parameter | Description |
+|-----------|------------|
+| `<str>`   | The string to calculate the length of |
+
+## Return value
+
+The length of the string <str>.
+
+## Example
+
+```sql
+select CHAR_LENGTH("abc"),CHAR_LENGTH("中国")
 ```
-### keywords
-    CHAR_LENGTH, CHARACTER_LENGTH
+
+```text
++-------------------------+----------------------------+
+| character_length('abc') | character_length('中国')   |
++-------------------------+----------------------------+
+|                       3 |                          2 |
++-------------------------+----------------------------+
+```

docs/sql-manual/sql-functions/scalar-functions/string-functions/char.md

@@ -24,44 +24,53 @@ specific language governing permissions and limitations
 under the License.
 -->
 
+## Description
 
-## function char
-### description
-#### Syntax
+Interpret each argument as an integer and return a string consisting of the characters given by the code values ​​of those integers. Special cases:
 
-`VARCHAR char(INT,..., [USING charset_name])`
+- If the result string is illegal for the given character set, the corresponding conversion result is NULL.
 
-Interprets each argument as an integer and returns a string consisting of the characters given by the code values of those integers. `NULL` values are skipped.
+- Arguments greater than `255` are converted to multiple result bytes. For example, `char(15049882)` is equivalent to `char(229, 164, 154)`.
 
-If the result string is illegal for the given character set, the result from `CHAR()` becomes `NULL`.
+## Description
 
-Arguments larger than `255` are converted into multiple result bytes. For example, `char(15049882)` is equivalent to `char(229, 164, 154)`.
+Interpret each argument as an integer and return a string consisting of the characters given by the code values ​​of those integers. Special cases:
 
-Currently only `utf8` is supported for `charset_name`.
+- If the result string is illegal for the given character set, the corresponding conversion results in the value NULL.
 
-### example
+- Arguments greater than `255` are converted to multiple result bytes. For example, `char(15049882)` is equivalent to `char(229, 164, 154)`.
 
+## Syntax
+
+```sql
+CHAR ( <expr> [ , <expr> ... ] [ USING <charset_name> ] )
 ```
-mysql> select char(68, 111, 114, 105, 115);
-+--------------------------------------+
-| char('utf8', 68, 111, 114, 105, 115) |
-+--------------------------------------+
-| Doris                                |
-+--------------------------------------+
-
-mysql> select char(15049882, 15179199, 14989469);
-+--------------------------------------------+
-| char('utf8', 15049882, 15179199, 14989469) |
-+--------------------------------------------+
-| 多睿丝                                     |
-+--------------------------------------------+
-
-mysql> select char(255);
-+-------------------+
-| char('utf8', 255) |
-+-------------------+
-| NULL              |
-+-------------------+
+
+## Parameters
+
+| Parameters       | Description |
+|------------------|---------------------|
+| `<expr>`         | Integer to be calculated as a character |
+| `<charset_name>` | Encoding of the return value, currently only supports `utf8` |
+
+## Return value
+
+Parameter list `<expr>` A string consisting of the corresponding characters. Special cases:
+
+- If the result string is illegal for the given character set, the corresponding conversion result is NULL.
+
+- Parameters greater than `255` will be converted to multiple result bytes. For example, `CHAR(15049882)` is equivalent to `CHAR(229, 164, 154)`.
+
+## Example
+
+```sql
+SELECT CHAR(68, 111, 114, 105, 115),CHAR(15049882, 15179199, 14989469),CHAR(255)
 ```
-### keywords
-    CHAR
+
+```text
++--------------------------------------+--------------------------------------------+-------------------+
+| char('utf8', 68, 111, 114, 105, 115) | char('utf8', 15049882, 15179199, 14989469) | char('utf8', 255) |
++--------------------------------------+--------------------------------------------+-------------------+
+| Doris                                | 多睿丝                                     | NULL              |
++--------------------------------------+--------------------------------------------+-------------------+
+```

docs/sql-manual/sql-functions/scalar-functions/string-functions/concat-ws.md

@@ -24,63 +24,61 @@ specific language governing permissions and limitations
 under the License.
 -->
 
-## concat_ws
-### Description
-#### Syntax
+## Description
+
+Use the first parameter sep as the connector to concatenate the second parameter and all subsequent parameters (or all strings in ARRAY) into a string. Special cases:
+
+- If the separator is NULL, NULL is returned.
+
+The `CONCAT_WS` function does not skip empty strings, but skips NULL values.
+
+## Syntax
 
 ```sql
-VARCHAR concat_ws(VARCHAR sep, VARCHAR str,...)
-VARCHAR concat_ws(VARCHAR sep, ARRAY array)
+CONCAT_WS ( <sep> , <str> [ , <str> ] )
+CONCAT_WS ( <sep> , <array> )
 ```
 
-Using the first parameter SEP as a connector, the second parameter and all subsequent parameters(or all string in an ARRAY) are spliced into a string.
-If the separator is NULL, return NULL.
-The `concat_ws` function does not skip empty strings, it skips NULL values.
+## Parameters
+
+| Parameter | Description |
+|-------|-----------------|
+| `<sep>` | Connector for concatenating strings |
+| `<str>` | String to be concatenated |
+| `<array>` | Array to be concatenated |
+
+## Return value
+
+Parameter `<sep>` or `<array>` The string concatenated with `<str>`. Special cases:
+
+- If delimiter is NULL, returns NULL.
 
-### example
+## Example
 
+Concatenate strings together using or
+
+```sql
+SELECT CONCAT_WS("or", "d", "is"),CONCAT_WS(NULL, "d", "is"),CONCAT_WS('or', 'd', NULL, 'is')
+```
+
+```text
++----------------------------+----------------------------+------------------------------------------+
+| concat_ws('or', 'd', 'is') | concat_ws(NULL, 'd', 'is') | concat_ws('or', 'd', NULL, 'is') |
++----------------------------+----------------------------+------------------------------------------+
+| doris                      | NULL                       | doris                              |
++----------------------------+----------------------------+------------------------------------------+
 ```
-mysql> select concat_ws("or", "d", "is");
-+----------------------------+
-| concat_ws('or', 'd', 'is') |
-+----------------------------+
-| doris                      |
-+----------------------------+
-
-mysql> select concat_ws(NULL, "d", "is");
-+----------------------------+
-| concat_ws(NULL, 'd', 'is') |
-+----------------------------+
-| NULL                       |
-+----------------------------+
-
-mysql> select concat_ws("or", "d", NULL,"is");
-+---------------------------------+
-| concat_ws("or", "d", NULL,"is") |
-+---------------------------------+
-| doris                           |
-+---------------------------------+
-
-mysql> select concat_ws("or", ["d", "is"]);
-+-----------------------------------+
-| concat_ws('or', ARRAY('d', 'is')) |
-+-----------------------------------+
-| doris                             |
-+-----------------------------------+
-
-mysql> select concat_ws(NULL, ["d", "is"]);
-+-----------------------------------+
-| concat_ws(NULL, ARRAY('d', 'is')) |
-+-----------------------------------+
-| NULL                              |
-+-----------------------------------+
-
-mysql> select concat_ws("or", ["d", NULL,"is"]);
-+-----------------------------------------+
-| concat_ws('or', ARRAY('d', NULL, 'is')) |
-+-----------------------------------------+
-| doris                                   |
-+-----------------------------------------+
+
+Concatenate array arrays together using or
+
+```sql
+SELECT CONCAT_WS("or", ["d", "is"]),CONCAT_WS(NULL, ["d", "is"]),CONCAT_WS("or", ["d", NULL,"is"])
 ```
-### keywords
-    CONCAT_WS,CONCAT,WS,ARRAY
+
+```text
++------------------------------+------------------------------+------------------------------------+
+| concat_ws('or', ['d', 'is']) | concat_ws(NULL, ['d', 'is']) | concat_ws('or', ['d', NULL, 'is']) |
++------------------------------+------------------------------+------------------------------------+
+| doris                        | NULL                         | doris                              |
++------------------------------+------------------------------+------------------------------------+
+```