Add CAST to DECIMAL with parameters to OQL docs

Author: dahfjkg

content/en/docs/refguide/modeling/domain-model/oql/oql-expression-syntax.md

@@ -738,6 +738,16 @@ The table below describes which `CAST` conversions are supported:
 
 Converting `DATETIME` or `BOOLEAN` to `STRING` returns different format per database.
 
+##### `DECIMAL` precision
+
+`DECIMAL` data type can have precision and scale as parameters:
+
+- `DECIMAL(<precision>, <scale>)` — in the case when both parameters are specified, those values are used as precision and scale of the resulting data type
+- `DECIMAL(<precision>)` — when only precision is specified, scaale is set to 0. The resulting data type in that case is `DECIMAL(<precision>, 0)`
+- `DECIMAL` — when no parameters are specified, default values are used. Precision is set to 28, and scale is set to 8: `DECIMAL(28, 8)`
+
+If the original value has more digits in the fractional part than required scale, the fractional part is rounded to the required scale. In that case, rounding is done according to the database configuration.
+
 #### Examples
 
 A frequent use case for `CAST` is to convert your date from the `DATETIME` data type to a text formatted `STRING` type:
@@ -758,6 +768,21 @@ SELECT (Number : 2) as Normal, (Cast(Number AS DECIMAL) : 2) as Casted FROM Sale
 | 1      | 1.0      |
 | 1      | 1.5    |
 
+In case of conversion to `DECIMAL`, scale and precision can be specified
+
+```sql
+SELECT
+	CAST('123.0987654321' AS DECIMAL) AS default_decimal,
+	CAST('123.0987654321' AS DECIMAL(20)) AS decimal_precision,
+	CAST('123.0987654321' AS DECIMAL(20, 6)) AS decimal_precision_scale
+FROM Sales.Order
+LIMIT 1
+```
+
+| default_decimal | decimal_precision  | decimal_precision_scale |        
+|------:|-------:|-------:|
+| 123.09876543      | 123    | 123.098765    |
+
 ### COALESCE {#coalesce-expression}
 
 Returns the value of the first `expression` that is not NULL. Can be used with columns.