From 3116ef3e79d50e4ace519f2a7cc22ff0609c7cfc Mon Sep 17 00:00:00 2001
From: Pavel Antoshin <pavel.antoshin@mendix.com>
Date: Fri, 13 Feb 2026 16:18:43 +0100
Subject: [PATCH] Document DATETRUNC

---
 .../domain-model/oql/oql-expression-syntax.md | 67 ++++++++++++++++++-
 1 file changed, 66 insertions(+), 1 deletion(-)

diff --git a/content/en/docs/refguide/modeling/domain-model/oql/oql-expression-syntax.md b/content/en/docs/refguide/modeling/domain-model/oql/oql-expression-syntax.md
index 0702ea87d6b..2baa445ef85 100644
--- a/content/en/docs/refguide/modeling/domain-model/oql/oql-expression-syntax.md
+++ b/content/en/docs/refguide/modeling/domain-model/oql/oql-expression-syntax.md
@@ -687,6 +687,7 @@ These are the currently supported functions:
 * COALESCE
 * DATEDIFF
 * DATEPART
+* DATETRUNC
 * LENGTH
 * LOWER
 * RANGEBEGIN
@@ -875,7 +876,7 @@ DATEDIFF ( unit , startdate_expression, enddate_expression [, timezone ] )
 * `MINUTE`,
 * `SECOND`
 * `MILLISECOND`.
-        
+
 For more information on `DATETIME` values, see the [example section under *DATEPART*](#oql-datepart-example), below.
 
 ##### startdate_expression
@@ -981,6 +982,70 @@ SELECT End FROM Sales.Period WHERE DATEPART(YEAR, End) = 2025
 |---------------------|
 | 2025-07-05 00:00:00 |
 
+### DATETRUNC {#datetrunc-function}
+
+The `DATETRUNC` function truncates a `DATETIME` value to a specified datepart. The return type is `DATETIME`.
+
+This function was introduced in Mendix version 11.9.0
+
+#### Syntax
+
+The syntax is as follows:
+
+```sql
+DATETRUNC ( datepart , date_expression [, timezone ] )
+```
+
+##### datepart
+
+`datepart` specifies the part to which the `DATETIME` value is truncated. For possible values, see the [Example](#oql-datetrunc-example) below.
+
+##### date_expression
+
+`date_expression` specifies the date to retrieve an element from. The expression should resolve to a `DATETIME` value. String representations of `DATETIME` are accepted.
+
+##### timezone
+
+`timezone` specifies the time zone to use for truncation. This parameter is optional and defaults to the local time zone. It should be a string literal containing an IANA time zone. GMT offset time zones are not supported.
+
+#### Examples{#oql-datetrunc-example}
+
+| datepart     | Truncation result for `2005-09-03T16:34:20.356` |
+|--------------|-------------------------------------------------|
+| `YEAR`       | `2005-01-01T00:00:00.000`                       |
+| `QUARTER`    | `2005-07-01T00:00:00.000`                       |
+| `MONTH`      | `2005-09-01T00:00:00.000`                       |
+| `DAY`        | `2005-09-03T00:00:00.000`                       |
+| `WEEK`*      | `2005-07-29T00:00:00.000`                       |
+| `HOUR`       | `2005-09-03T16:00:00.000`                       |
+| `MINUTE`     | `2005-09-03T16:34:00.000`                       |
+| `SECOND`     | `2005-09-03T16:34:20.000`                       |
+
+{{% alert color="info" %}}
+Date part types `DAYOFYEAR`, `WEEKDAY` and `MILLISECOND` are not supported by the `DATETRUNC` function
+{{% /alert %}}
+
+{{% alert color="info" %}}
+For the date part type `WEEK`, the result of the `DATETRUNC` function depends on the database configuration. For example, by default, the first day of the week in MS SQL Server is Sunday, which means that dates are truncated to previos Sunday if date part type `WEEK` is used.
+{{% /alert %}}
+
+`DATETRUNC` function can be used to group data by time periods:
+
+```sql
+SELECT
+	DATETRUNC(QUARTER, End) AS PeriodEndQuarter,
+	SUM(Revenue) AS QuarterPeriodRevenue
+FROM
+	Sales.Period
+GROUP BY
+	DATETRUNC(QUARTER, End)
+```
+
+|  PeriodEndQuarter   | QuarterPeriodRevenue |
+|---------------------|----------------------|
+| 2024-04-01 00:00:00 | 10                   |
+| 2025-07-01 00:00:00 | 28                   |
+
 ### LENGTH {#length-function}
 
 #### Description