Hello,

I have attempted DP-900 Exam on 05th October 2020. and cleared the exam with 850 marks. Here is my preparation guide. The below-provided materials are enough to clear this exam with a flying score.

You have to be clear in below topics

i) Data, visualization, Types of charts

ii) Relational Database

* SQL on Virtual Machine
* Azure Managed instance
* Azure SQL database
* Azure Mysql database
* Azure Postgres database
* Azure MariaDB 

iii) Non-Relational Database (NoSQL)

 *  Azure Cosmos DB
 *  Azure Table Storage
 *  Azure Document DB
 *  Graph Database
 *  Column Database
 *  Blob Storage

iv) OLTP vs OLAP

v) Azure synapse database, Azure DataLake

vi) Data factory, Databricks

vii) PowerBi (just an overview of it and its services)

Preparation path:

1) Microsoft Learning Path for DP-900

https://docs.microsoft.com/en-us/learn/certifications/exams/dp-900/

2) Scott Duffy DP-900 course on udemy

https://www.udemy.com/course/dp900-azure/

3) Exam topics practise tests.

These 3 resources are enough to excel in your exam.

Good Luck and all the very best!!