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new d847a93b5a1 [Doc] add REGEXP_EXTRACT_OR_NULL docs (#2437)
d847a93b5a1 is described below
commit d847a93b5a1e8127a6d9653915e55ca79be67019
Author: zclllyybb <zhaochan...@selectdb.com>
AuthorDate: Tue Jun 10 22:50:45 2025 +0800
[Doc] add REGEXP_EXTRACT_OR_NULL docs (#2437)
## Versions
- [x] dev
- [x] 3.0
- [x] 2.1
- [ ] 2.0
## Languages
- [x] Chinese
- [x] English
---
.../string-functions/regexp-extract-or-null.md | 90 +++++++++++++++++++++
.../string-functions/regexp-extract-or-null.md | 90 +++++++++++++++++++++
.../string-functions/regexp-extract-or-null.md | 94 ++++++++++++++++++++++
.../string-functions/regexp-extract-or-null.md | 94 ++++++++++++++++++++++
.../string-functions/regexp-extract-or-null.md | 94 ++++++++++++++++++++++
.../string-functions/regexp-extract-or-null.md | 94 ++++++++++++++++++++++
6 files changed, 556 insertions(+)
diff --git
a/docs/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
b/docs/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
index 103fbbdc247..b32635ece27 100644
---
a/docs/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
+++
b/docs/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
@@ -21,3 +21,93 @@ KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
+
+## Description
+
+Extract the first substring that matches the target regular expression pattern
from the text string, and extract a specific group from it based on the
expression group index.
+
+- Character set matching requires the use of Unicode standard character types.
For example, to match Chinese characters, use `\p{Han}`.
+
+## Syntax
+
+```sql
+REGEXP_EXTRACT_OR_NULL(<str>, <pattern>, <pos>)
+```
+
+## Parameters
+
+| Parameter | Description |
+| -- | -- |
+| `<str>` | String, a text string that needs to be matched with regular
expressions. |
+| `<pattern>` | String, target pattern. |
+| `<pos>` | Integer, the index of the expression group to extract, counting
starts from 1. |
+
+## Return Value
+
+Return a string type, with the result being the part that matches `<pattern>`.
+
+- If the input `<pos>` is 0, return the entire first matching substring.
+- If the input `<pos>` is invalid (negative or exceeds the number of
expression groups), return NULL.
+- If the regular expression fails to match, return NULL.
+
+## Example
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
1);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 1) |
++---------------------------------------------------------------------------+
+| b |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
0);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 0) |
++---------------------------------------------------------------------------+
+| bCd |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
5);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 5) |
++---------------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1);
+```
+
+```text
++---------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1) |
++---------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------+
+```
+
+```sql
+select REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2);
+```
+
+```text
++---------------------------------------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2) |
++---------------------------------------------------------------------------------------------------------+
+| This is a passage in English 1234567
|
++---------------------------------------------------------------------------------------------------------+
+```
diff --git
a/i18n/zh-CN/docusaurus-plugin-content-docs/current/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
b/i18n/zh-CN/docusaurus-plugin-content-docs/current/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
index 103fbbdc247..063952eb21e 100644
---
a/i18n/zh-CN/docusaurus-plugin-content-docs/current/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
+++
b/i18n/zh-CN/docusaurus-plugin-content-docs/current/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
@@ -21,3 +21,93 @@ KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
+
+## 描述
+
+提取文本串中最先出现的与目标正则模式匹配的子串，并根据表达式组下标提取其中的特定组。
+
+- 字符集匹配需要使用 Unicode 标准字符类型。例如，匹配中文请使用 `\p{Han}`。
+
+## 语法
+
+```sql
+REGEXP_EXTRACT_OR_NULL(<str>, <pattern>, <pos>)
+```
+
+## 参数
+
+| 参数 | 描述 |
+| -- | -- |
+| `<str>` | 字符串，需要进行正则匹配的文本串。|
+| `<pattern>` | 字符串，目标模式。|
+| `<pos>` | 整数，要提取的表达式组下标，从 1 开始计数。 |
+
+## 返回值
+
+返回字符串类型，结果为匹配 `<pattern>` 的部分。
+
+- 如果输入的 `<pos>` 为 0，返回整个第一次匹配的子文本串。
+- 如果输入的 `<pos>` 不合法（为负数或超出表达式组数量），返回 NULL。
+- 如果正则匹配失败，返回 NULL。
+
+## 举例
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
1);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 1) |
++---------------------------------------------------------------------------+
+| b |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
0);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 0) |
++---------------------------------------------------------------------------+
+| bCd |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
5);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 5) |
++---------------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1);
+```
+
+```text
++---------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1) |
++---------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------+
+```
+
+```sql
+select REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2);
+```
+
+```text
++---------------------------------------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2) |
++---------------------------------------------------------------------------------------------------------+
+| This is a passage in English 1234567
|
++---------------------------------------------------------------------------------------------------------+
+```
diff --git
a/i18n/zh-CN/docusaurus-plugin-content-docs/version-2.1/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
b/i18n/zh-CN/docusaurus-plugin-content-docs/version-2.1/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
index 103fbbdc247..9847056dbec 100644
---
a/i18n/zh-CN/docusaurus-plugin-content-docs/version-2.1/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
+++
b/i18n/zh-CN/docusaurus-plugin-content-docs/version-2.1/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
@@ -21,3 +21,97 @@ KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
+
+## 描述
+
+提取文本串中最先出现的与目标正则模式匹配的子串，并根据表达式组下标提取其中的特定组。
+
+- 字符集匹配需要使用 Unicode 标准字符类型。例如，匹配中文请使用 `\p{Han}`。
+
+:::info
+自 Doris 2.1.6 起支持
+:::
+
+## 语法
+
+```sql
+REGEXP_EXTRACT_OR_NULL(<str>, <pattern>, <pos>)
+```
+
+## 参数
+
+| 参数 | 描述 |
+| -- | -- |
+| `<str>` | 字符串，需要进行正则匹配的文本串。|
+| `<pattern>` | 字符串，目标模式。|
+| `<pos>` | 整数，要提取的表达式组下标，从 1 开始计数。 |
+
+## 返回值
+
+返回字符串类型，结果为匹配 `<pattern>` 的部分。
+
+- 如果输入的 `<pos>` 为 0，返回整个第一次匹配的子文本串。
+- 如果输入的 `<pos>` 不合法（为负数或超出表达式组数量），返回 NULL。
+- 如果正则匹配失败，返回 NULL。
+
+## 举例
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
1);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 1) |
++---------------------------------------------------------------------------+
+| b |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
0);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 0) |
++---------------------------------------------------------------------------+
+| bCd |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
5);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 5) |
++---------------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1);
+```
+
+```text
++---------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1) |
++---------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------+
+```
+
+```sql
+select REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2);
+```
+
+```text
++---------------------------------------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2) |
++---------------------------------------------------------------------------------------------------------+
+| This is a passage in English 1234567
|
++---------------------------------------------------------------------------------------------------------+
+```
diff --git
a/i18n/zh-CN/docusaurus-plugin-content-docs/version-3.0/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
b/i18n/zh-CN/docusaurus-plugin-content-docs/version-3.0/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
index 103fbbdc247..acd70e05a2e 100644
---
a/i18n/zh-CN/docusaurus-plugin-content-docs/version-3.0/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
+++
b/i18n/zh-CN/docusaurus-plugin-content-docs/version-3.0/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
@@ -21,3 +21,97 @@ KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
+
+## 描述
+
+提取文本串中最先出现的与目标正则模式匹配的子串，并根据表达式组下标提取其中的特定组。
+
+- 字符集匹配需要使用 Unicode 标准字符类型。例如，匹配中文请使用 `\p{Han}`。
+
+:::info
+自 Doris 3.0.2 起支持
+:::
+
+## 语法
+
+```sql
+REGEXP_EXTRACT_OR_NULL(<str>, <pattern>, <pos>)
+```
+
+## 参数
+
+| 参数 | 描述 |
+| -- | -- |
+| `<str>` | 字符串，需要进行正则匹配的文本串。|
+| `<pattern>` | 字符串，目标模式。|
+| `<pos>` | 整数，要提取的表达式组下标，从 1 开始计数。 |
+
+## 返回值
+
+返回字符串类型，结果为匹配 `<pattern>` 的部分。
+
+- 如果输入的 `<pos>` 为 0，返回整个第一次匹配的子文本串。
+- 如果输入的 `<pos>` 不合法（为负数或超出表达式组数量），返回 NULL。
+- 如果正则匹配失败，返回 NULL。
+
+## 举例
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
1);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 1) |
++---------------------------------------------------------------------------+
+| b |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
0);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 0) |
++---------------------------------------------------------------------------+
+| bCd |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
5);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 5) |
++---------------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1);
+```
+
+```text
++---------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1) |
++---------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------+
+```
+
+```sql
+select REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2);
+```
+
+```text
++---------------------------------------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2) |
++---------------------------------------------------------------------------------------------------------+
+| This is a passage in English 1234567
|
++---------------------------------------------------------------------------------------------------------+
+```
diff --git
a/versioned_docs/version-2.1/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
b/versioned_docs/version-2.1/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
index 103fbbdc247..742f28d9bfc 100644
---
a/versioned_docs/version-2.1/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
+++
b/versioned_docs/version-2.1/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
@@ -21,3 +21,97 @@ KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
+
+## Description
+
+Extract the first substring that matches the target regular expression pattern
from the text string, and extract a specific group from it based on the
expression group index.
+
+- Character set matching requires the use of Unicode standard character types.
For example, to match Chinese characters, use `\p{Han}`.
+
+:::info
+Support since Apache Doris 2.1.6
+:::
+
+## Syntax
+
+```sql
+REGEXP_EXTRACT_OR_NULL(<str>, <pattern>, <pos>)
+```
+
+## Parameters
+
+| Parameter | Description |
+| -- | -- |
+| `<str>` | String, a text string that needs to be matched with regular
expressions. |
+| `<pattern>` | String, target pattern. |
+| `<pos>` | Integer, the index of the expression group to extract, counting
starts from 1. |
+
+## Return Value
+
+Return a string type, with the result being the part that matches `<pattern>`.
+
+- If the input `<pos>` is 0, return the entire first matching substring.
+- If the input `<pos>` is invalid (negative or exceeds the number of
expression groups), return NULL.
+- If the regular expression fails to match, return NULL.
+
+## Example
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
1);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 1) |
++---------------------------------------------------------------------------+
+| b |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
0);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 0) |
++---------------------------------------------------------------------------+
+| bCd |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
5);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 5) |
++---------------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1);
+```
+
+```text
++---------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1) |
++---------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------+
+```
+
+```sql
+select REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2);
+```
+
+```text
++---------------------------------------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2) |
++---------------------------------------------------------------------------------------------------------+
+| This is a passage in English 1234567
|
++---------------------------------------------------------------------------------------------------------+
+```
diff --git
a/versioned_docs/version-3.0/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
b/versioned_docs/version-3.0/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
index 103fbbdc247..a326d795ddd 100644
---
a/versioned_docs/version-3.0/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
+++
b/versioned_docs/version-3.0/sql-manual/sql-functions/scalar-functions/string-functions/regexp-extract-or-null.md
@@ -21,3 +21,97 @@ KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
+
+## Description
+
+Extract the first substring that matches the target regular expression pattern
from the text string, and extract a specific group from it based on the
expression group index.
+
+- Character set matching requires the use of Unicode standard character types.
For example, to match Chinese characters, use `\p{Han}`.
+
+:::info
+Support since Apache Doris 3.0.2
+:::
+
+## Syntax
+
+```sql
+REGEXP_EXTRACT_OR_NULL(<str>, <pattern>, <pos>)
+```
+
+## Parameters
+
+| Parameter | Description |
+| -- | -- |
+| `<str>` | String, a text string that needs to be matched with regular
expressions. |
+| `<pattern>` | String, target pattern. |
+| `<pos>` | Integer, the index of the expression group to extract, counting
starts from 1. |
+
+## Return Value
+
+Return a string type, with the result being the part that matches `<pattern>`.
+
+- If the input `<pos>` is 0, return the entire first matching substring.
+- If the input `<pos>` is invalid (negative or exceeds the number of
expression groups), return NULL.
+- If the regular expression fails to match, return NULL.
+
+## Example
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
1);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 1) |
++---------------------------------------------------------------------------+
+| b |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
0);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 0) |
++---------------------------------------------------------------------------+
+| bCd |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)',
5);
+```
+
+```text
++---------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('123AbCdExCx', '([[:lower:]]+)C([[:lower:]]+)', 5) |
++---------------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------------+
+```
+
+```sql
+SELECT REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1);
+```
+
+```text
++---------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('AbCdE', '([[:lower:]]+)C([[:upper:]]+)', 1) |
++---------------------------------------------------------------------+
+| NULL |
++---------------------------------------------------------------------+
+```
+
+```sql
+select REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2);
+```
+
+```text
++---------------------------------------------------------------------------------------------------------+
+| REGEXP_EXTRACT_OR_NULL('这是一段中文 This is a passage in English 1234567',
'(\\p{Han}+)(.+)', 2) |
++---------------------------------------------------------------------------------------------------------+
+| This is a passage in English 1234567
|
++---------------------------------------------------------------------------------------------------------+
+```
---------------------------------------------------------------------
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