How can you compare data across multiple databases?

1 Use SQL queries

One of the most basic and powerful methods to compare data across multiple databases is to use SQL queries. SQL, or Structured Query Language, is a standard language for manipulating and querying data in relational databases. You can use SQL to join, filter, aggregate, and compare data from different tables and databases, as long as they share a common key or attribute. For example, you can use a SQL query like this to compare the sales of two products from two different databases:

SELECT p1.product_name, p1.sales, p2.product_name, p2.sales
FROM database1.products p1
INNER JOIN database2.products p2
ON p1.product_id = p2.product_id
WHERE p1.product_name = 'Product A' OR p2.product_name = 'Product B';        

This query will return the product names and sales from both databases for Product A and Product B, which have the same product_id in both databases. You can then use this data to create charts, tables, or dashboards to visualize the comparison.

2 Use ETL tools

Another method to compare data across multiple databases is to use ETL tools. ETL, or Extract, Transform, and Load, is a process of extracting data from different sources, transforming it into a common format, and loading it into a target destination, such as a data warehouse or a data lake. ETL tools are software applications that automate and simplify the ETL process, allowing you to connect to different databases, apply transformations, and load the data into a single repository. Some examples of ETL tools are Talend, Informatica, and SSIS. By using ETL tools, you can create a unified and consistent view of your data from different databases, and then use BI tools to compare and analyze the data.

3 Use BI tools

A third method to compare data across multiple databases is to use BI tools. BI tools are software applications that enable you to access, analyze, and visualize data from different sources, such as databases, files, APIs, or web services. Some examples of BI tools are Tableau, Power BI, and Qlik. By using BI tools, you can connect to multiple databases, create queries, apply filters, and create charts, tables, or dashboards to compare and display the data. BI tools also offer features such as data blending, data modeling, and data storytelling, which can help you compare data across multiple databases more effectively and intuitively.

Comparing data across multiple databases is a key skill for BI professionals who want to gain insights from different data sources. By using SQL queries, ETL tools, or BI tools, you can access, integrate, and visualize data from different databases and generate reports and dashboards that can support your decision making and business goals.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?