[doc]Fix string function documentation docs

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

@@ -22,86 +22,89 @@ specific language governing permissions and limitations
 under the License.
 -->
 
-## count_substrings
+## Description
 
-### description
+The COUNT_SUBSTRINGS function counts the number of occurrences of a specified substring within a string. Note: The current implementation continues searching after shifting by the length of the substring when a match is found. For example, when str='ccc' and pattern='cc', the result returned is 1.
 
-#### Syntax
+## Syntax
 
-`int count_substrings(STRING str, STRING pattern)`
-Returns the total number of occurrences of the substring pattern in the string str.
-Note: The current implementation shifts by the length of the pattern after each match in the string.
-Therefore, when str: ccc and pattern: cc, the result returned is 1.
-
-#### Arguments
+```sql
+COUNT_SUBSTRINGS(<str>, <pattern>)
+```
 
-`str` — The string to be checked. Type: `String`
-`pattern` — The substring to be matched. Type: `String`
+## Parameters
+| Parameter | Description                             |
+| --------- | --------------------------------------- |
+| `<str>` | The string to be searched. Type: STRING |
+| `<pattern>` | The substring to match. Type: STRING    |
 
+## Return Value
 
-#### Returned value(s)
+Returns an INT type, representing the number of times the substring appears in the string.
 
-Returns the total number of occurrences of the substring.
+Special cases:
+- If str is NULL, returns NULL
+- If pattern is an empty string, returns 0
+- If str is an empty string, returns 0
 
-### example
+## Examples
 
+1. Basic usage
+```sql
+SELECT count_substrings('a1b1c1d', '1');
 ```
-mysql [(none)]>select count_substrings('a1b1c1d','1');
+```text
 +----------------------------------+
 | count_substrings('a1b1c1d', '1') |
 +----------------------------------+
 |                                3 |
 +----------------------------------+
+```
 
-mysql [(none)]>select count_substrings(',,a,b,c,',',');
+2. Case with consecutive commas
+```sql
+SELECT count_substrings(',,a,b,c,', ',');
+```
+```text
 +-----------------------------------+
 | count_substrings(',,a,b,c,', ',') |
 +-----------------------------------+
 |                                 5 |
 +-----------------------------------+
+```
 
-mysql [(none)]>select count_substrings('ccc','cc');
+3. Case with overlapping substrings
+```sql
+SELECT count_substrings('ccc', 'cc');
+```
+```text
 +--------------------------------+
 | count_substrings('ccc', 'cc')  |
 +--------------------------------+
 |                              1 |
 +--------------------------------+
+```
 
-mysql [(none)]>SELECT count_substrings(NULL,',');
+4. NULL value handling
+```sql
+SELECT count_substrings(NULL, ',');
+```
+```text
 +-----------------------------+
 | count_substrings(NULL, ',') |
 +-----------------------------+
 |                        NULL |
 +-----------------------------+
+```
 
-mysql [(none)]>select count_substrings('a,b,c,abcde','');
+5. Empty string handling
+```sql
+SELECT count_substrings('a,b,c,abcde', '');
+```
+```text
 +-------------------------------------+
 | count_substrings('a,b,c,abcde', '') |
 +-------------------------------------+
 |                                   0 |
 +-------------------------------------+
-
-mysql [(none)]>select count_substrings(NULL, 'a');
-+-----------------------------+
-| count_substrings(NULL, 'a') |
-+-----------------------------+
-|                        NULL |
-+-----------------------------+
-
-mysql [(none)]>select count_substrings('','asd');
-+-----------------------------+
-| count_substrings('', 'asd') |
-+-----------------------------+
-|                           0 |
-+-----------------------------+
-
-mysql [(none)]>select count_substrings('abccbaacb','c');
-+------------------------------------+
-| count_substrings('abccbaacb', 'c') |
-+------------------------------------+
-|                                  3 |
-+------------------------------------+
-```
-### keywords
-
-COUNT_SUBSTRINGS,SUBSTRINGS
+```

docs/sql-manual/sql-functions/scalar-functions/string-functions/cut-to-first-significant-subdomain.md

@@ -24,40 +24,63 @@ specific language governing permissions and limitations
 under the License.
 -->
 
-
 ## Description
 
+The CUT_TO_FIRST_SIGNIFICANT_SUBDOMAIN function extracts the effective part of a domain from a URL, including the top-level domain up to the "first significant subdomain". If the input URL is invalid, it returns an empty string.
+
 ## Syntax
 
-`VARCHAR  cut_to_first_significant_subdomain(VARCHAR url)`
+```sql
+CUT_TO_FIRST_SIGNIFICANT_SUBDOMAIN(<url>)
+```
+
+## Parameters
+| Parameter | Description                                   |
+| --------- | --------------------------------------------- |
+| `<url>` | The URL string to be processed. Type: VARCHAR |
 
-Extract the part of the domain in the URL from the top-level subdomain down to the "first valid subdomain." If invalid, return an empty string.
+## Return Value
+
+Returns VARCHAR type, representing the extracted domain part.
+
+Special cases:
+- If url is NULL, returns NULL
+- If url is not a valid domain format, returns an empty string
 
 ## Examples
 
+1. Basic domain processing
 ```sql
-mysql [(none)]>select cut_to_first_significant_subdomain("www.baidu.com");
+SELECT cut_to_first_significant_subdomain('www.baidu.com');
+```
+```text
 +-----------------------------------------------------+
 | cut_to_first_significant_subdomain('www.baidu.com') |
 +-----------------------------------------------------+
 | baidu.com                                           |
 +-----------------------------------------------------+
+```
 
-mysql [(none)]>select cut_to_first_significant_subdomain("www.google.com.cn");
+2. Multi-level domain processing
+```sql
+SELECT cut_to_first_significant_subdomain('www.google.com.cn');
+```
+```text
 +---------------------------------------------------------+
 | cut_to_first_significant_subdomain('www.google.com.cn') |
 +---------------------------------------------------------+
 | google.com.cn                                           |
 +---------------------------------------------------------+
+```
 
-mysql [(none)]>select cut_to_first_significant_subdomain("wwwwwwww");
+3. Invalid domain processing
+```sql
+SELECT cut_to_first_significant_subdomain('wwwwwwww');
+```
+```text
 +------------------------------------------------+
 | cut_to_first_significant_subdomain('wwwwwwww') |
 +------------------------------------------------+
 |                                                |
 +------------------------------------------------+
-```
-
-### Keywords
-
-CUT_TO_FIRST_SIGNIFICANT_SUBDOMAIN
+```

docs/sql-manual/sql-functions/scalar-functions/string-functions/ltrim-in.md

@@ -27,31 +27,64 @@ under the License.
 
 ## Description
 
+The LTRIM_IN function removes specified characters from the left side of a string. When no character set is specified, it removes leading spaces by default. When a character set is specified, it removes all specified characters from the left side (regardless of their order in the set).
+The key feature of LTRIM_IN is that it removes any combination of characters from the specified set, while the LTRIM function removes characters based on exact string matching.
 
 ## Syntax
 
-`VARCHAR ltrim_in(VARCHAR str[, VARCHAR rhs])`
+```sql
+LTRIM_IN(<str> [, <rhs>])
+```
+
+## Parameters
+| Parameter | Description                                                            |
+| --------- | ---------------------------------------------------------------------- |
+| `<str>` | The string to be processed. Type: VARCHAR                              |
+| `<rhs>` | Optional parameter, the set of characters to be removed. Type: VARCHAR |
 
-When there is no rhs parameter, remove the spaces that appear consecutively in the parameter str starting from the left part; when there is an rhs parameter, search and remove any characters in the rhs character set at the left end of the string (regardless of order)
+## Return Value
+
+Returns VARCHAR type, representing the processed string.
+
+Special cases:
+- If str is NULL, returns NULL
+- If rhs is not specified, removes all leading spaces
+- If rhs is specified, removes all characters from the left side that appear in rhs until encountering the first character not in rhs
 
 ## Examples
 
+1. Remove leading spaces
 ```sql
-mysql> SELECT ltrim_in('   ab d') str;
+SELECT ltrim_in('   ab d') str;
+```
+```text
 +------+
 | str  |
 +------+
 | ab d |
 +------+
+```
 
-mysql> SELECT ltrim_in('ababccaab','ab') str;
+2. Remove specified character set
+```sql
+SELECT ltrim_in('ababccaab', 'ab') str;
+```
+```text
 +-------+
 | str   |
 +-------+
 | ccaab |
 +-------+
 ```
 
-## Keywords
-
-LTRIM_IN
+3. Comparison with LTRIM function
+```sql
+SELECT ltrim_in('abcd', 'ae'),ltrim('abcd', 'abe');
+```
+```text
++------------------------+----------------------+
+| ltrim_in('abcd', 'ae') | ltrim('abcd', 'abe') |
++------------------------+----------------------+
+| bcd                    | abcd                 |
++------------------------+----------------------+
+```

docs/sql-manual/sql-functions/scalar-functions/string-functions/rtrim-in.md

@@ -27,33 +27,65 @@ under the License.
 
 ## Description
 
+The RTRIM_IN function removes specified characters from the right side of a string. When no character set is specified, it removes trailing spaces by default. When a character set is specified, it removes all specified characters from the right side (regardless of their order in the set).
+The key feature of RTRIM_IN is that it removes any combination of characters from the specified set, while the RTRIM function removes characters based on exact string matching.
 
 ## Syntax
 
-`VARCHAR rtrim_in(VARCHAR str[, VARCHAR rhs])`
+```sql
+RTRIM_IN(<str>[, <rhs>])
+```
+
+## Parameters
+| Parameter | Description                                                            |
+| --------- | ---------------------------------------------------------------------- |
+| `<str>` | The string to be processed. Type: VARCHAR                              |
+| `<rhs>` | Optional parameter, the set of characters to be removed. Type: VARCHAR |
 
-When there is no rhs parameter, remove the spaces that appear consecutively in the parameter str starting from the right part; when there is an rhs parameter, search and remove any characters in the rhs character set at the right end of the string (regardless of order)
+## Return Value
 
+Returns VARCHAR type, representing the processed string.
 
+Special cases:
+- If str is NULL, returns NULL
+- If rhs is not specified, removes all trailing spaces
+- If rhs is specified, removes all characters from the right side that appear in rhs until encountering the first character not in rhs
 
-## Example
+## Examples
 
+1. Remove trailing spaces
 ```sql
-mysql> SELECT rtrim_in('ab d   ') str;
+SELECT rtrim_in('ab d   ') str;
+```
+```text
 +------+
 | str  |
 +------+
 | ab d |
 +------+
-
-mysql> SELECT rtrim_in('ababccaab','ab') str;
-+--------+
-| str    |
-+--------+
-| ababcc |
-+--------+
 ```
 
-## Keywords
+2. Remove specified character set
+```sql
+-- RTRIM_IN removes any 'a' and 'b' characters from the right end
+SELECT rtrim_in('ababccaab', 'ab') str;
+```
+```text
++---------+
+| str     |
++---------+
+| ababcc  |
++---------+
+```
 
-RTRIM_IN
+3. Comparison with RTRIM function
+```sql
+SELECT rtrim_in('ababccaab', 'ab'),rtrim('ababccaab', 'ab');
+```
+```text
++-----------------------------+--------------------------+
+| rtrim_in('ababccaab', 'ab') | rtrim('ababccaab', 'ab') |
++-----------------------------+--------------------------+
+| ababcc                      | ababcca                  |
++-----------------------------+--------------------------+
+```