Merge branch 'patch-5' of https://github.com/pabechevb/sql-docs into 20211129-external-table

Author: MikeRayMSFT

docs/relational-databases/polybase/polybase-configure-mongodb.md

@@ -31,7 +31,8 @@ To query the data from a MongoDB data source, you must create external tables to
 The following Transact-SQL commands are used in this section:
 
 - [CREATE DATABASE SCOPED CREDENTIAL (Transact-SQL)](../../t-sql/statements/create-database-scoped-credential-transact-sql.md)
-- [CREATE EXTERNAL DATA SOURCE (Transact-SQL)](../../t-sql/statements/create-external-data-source-transact-sql.md) 
+- [CREATE EXTERNAL DATA SOURCE (Transact-SQL)](../../t-sql/statements/create-external-data-source-transact-sql.md)
+- [CREATE EXTERNAL TABLE (Transact-SQL)](../../t-sql/statements/create-external-table-transact-sql.md)
 - [CREATE STATISTICS (Transact-SQL)](../../t-sql/statements/create-statistics-transact-sql.md)
 
 1. Create a database scoped credential for accessing the MongoDB source.
@@ -66,6 +67,24 @@ The following Transact-SQL commands are used in this section:
     [ ; ]
     ```
 
+1. Create an external table.
+
+    The following script creates te external table. For reference, see [CREATE EXTERNAL TABLE](../../t-sql/statements/create-external-table-transact-sql.md). Before you run the script update it for your environment:
+    
+    - Update the fields with their name, collation, and if they are collections then specify the colection name and the field name, note "friends" is a custom data type.
+    - Update the location. Set the database name and the table name. Note three-part names are not allowed, so you can't create it for the system.profile table. Also you can't specify a view because it can't obtain the metadata from it.
+    - Update the data source with the name of the one you created in the previous step.
+    
+    ```sql
+    CREATE EXTERNAL TABLE [MongoDbRandomData](
+      [_id] NVARCHAR(24) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
+      [RandomData_friends_id] INT,
+      [RandomData_tags] NVARCHAR(MAX) COLLATE SQL_Latin1_General_CP1_CI_AS)
+    WITH (
+      LOCATION='MyDb.RandomData',
+      DATA_SOURCE=[MongoDb])
+    ```
+
 1. **Optional:** Create statistics on an external table.
 
     We recommend creating statistics on external table columns, especially the ones used for joins, filters and aggregates, for optimal query performance.