docs: Misc fixes. Closes #7286 and #7532

Author: igorlukanin

docs/pages/product/data-modeling/syntax.mdx

@@ -139,6 +139,13 @@ cube(`orders`, {
 
 </CodeTabs>
 
+### User-defined functions
+
+If you have created a [user-defined function][link-sql-udf] (UDF) in your data
+source, you can use it in the `sql` parameter as well.
+
+### Case sensitivity
+
 If your database uses case-sensitive identifiers, make sure to properly
 quote table and column names. For example, here's how you can reference
 a Postgres table that contains uppercase letters in its name:
@@ -570,4 +577,5 @@ defining dynamic data models.
 [wiki-snake-case]: https://en.wikipedia.org/wiki/Snake_case
 [wiki-yaml]: https://en.wikipedia.org/wiki/YAML
 [link-snowflake-listagg]: https://docs.snowflake.com/en/sql-reference/functions/listagg
-[link-bigquery-stringagg]: https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#string_agg
+[link-bigquery-stringagg]: https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#string_agg
+[link-sql-udf]: https://en.wikipedia.org/wiki/User-defined_function#Databases

docs/pages/product/getting-started/cloud/create-data-model.mdx

@@ -55,7 +55,7 @@ cubes:
 
     joins:
       - name: users
-        sql: "{CUBE}.USER_ID = {users}.USER_ID"
+        sql: "{CUBE}.USER_ID = {users}.ID"
         relationship: many_to_one
 
     dimensions:
@@ -127,7 +127,7 @@ cubes:
 
     joins:
       - name: users
-        sql: "{CUBE}.USER_ID = {users}.USER_ID"
+        sql: "{CUBE}.USER_ID = {users}.ID"
         relationship: many_to_one
 
     dimensions:

docs/pages/product/getting-started/cloud/load-data.mdx

@@ -69,7 +69,6 @@ Run the following command to create the `users` table.
 ```sql
 CREATE TABLE cube_demo.ecom.users
 ( id INTEGER,
-  user_id INTEGER,
   city VARCHAR,
   age INTEGER,
   gender VARCHAR,

docs/pages/reference/data-model/pre-aggregations.mdx

@@ -986,6 +986,13 @@ existing tables.
 
 </WarningBox>
 
+<WarningBox>
+
+Because incremental refreshes generate their own SQL, you **must not** use the
+[`sql`](#parameters-refresh-key-sql) property here.
+
+</WarningBox>
+
 <CodeTabs>
 
 ```javascript