sql regexp functions (#4774)

content/influxdb/cloud-iox/reference/sql/functions/regular-expression.md

@@ -0,0 +1,74 @@
+---
+title: SQL regular expression functions
+list_title: Regular expression functions
+description: >
+  Use regular expression functions to operate on data in SQL queries.
+menu:
+  influxdb_cloud_iox:
+    name: Regular expression
+    parent: sql-functions    
+weight: 308
+influxdb/cloud-iox/tags: [regular expressions, sql]
+---
+
+The InfluxDB SQL implementation uses the POSIX regular expression syntax and
+supports the following regular expression functions:
+
+<!-- - [regexp_match](#regexp_match) -->
+- [regexp_replace](#regexp_replace)
+
+<!--
+
+## regexp_match
+
+Returns a list of regular expression matches in a string.
+
+```sql
+regexp_match(str, regexp)
+```
+
+##### Arguments
+
+- **str**: String column or literal string to operate on.
+- **regexp**: Regular expression to match against.
+
+-->
+
+## regexp_replace
+
+Replaces substrings in a string that match a regular expression.
+
+```sql
+regexp_replace(str, regexp, replacement, flags)
+```
+
+##### Arguments
+
+- **str**: String column or literal string to operate on.
+- **regexp**: Regular expression to match against.
+- **replacement**: Replacement string.
+- **flags**: Regular expression flags that control the behavior of the
+  regular expression. The following flags are supported.
+  - **g**: (global) Search globally and don't return after the first match.
+  - **i**: (insensitive) Ignore case when matching.
+
+{{< expand-wrapper >}}
+{{% expand "View `regexp_replace` query example" %}}
+
+_The following example uses the sample data set provided in
+[Get started with InfluxDB tutorial](/influxdb/cloud-iox/get-started/write/#construct-line-protocol)._
+
+```sql
+SELECT DISTINCT
+  room,
+  regexp_replace(room::STRING, '\sRoom', '', 'gi') AS regexp_replace
+FROM home
+```
+
+| room        | regexp_replace |
+| :---------- | :------------- |
+| Kitchen     | Kitchen        |
+| Living Room | Living         |
+
+{{% /expand %}}
+{{< /expand-wrapper >}}