What is Import and Direct Query in Power BI?

Choosing how to connect to your data in Power BI is one of the first, and most important, decisions you'll make when building a report. The storage mode you select - primarily Import or DirectQuery - dictates your report's performance, data freshness, and the complexity you can handle. This guide will break down the key differences between these two modes to help you confidently pick the right one for your projects.

The Fundamental Difference: Where Does Your Data Live?

At its core, the choice between Import and DirectQuery comes down to a simple question: do you want to copy the data into Power BI, or keep the data in its original source and have Power BI query it live?

• Import Mode: Power BI takes a full copy of your data from the source and loads it into its internal, high-performance in-memory engine (called the VertiPaq engine). Your report then interacts with this compressed, cached copy.
• DirectQuery Mode: No data is copied into Power BI. Instead, Power BI acts as a visualization layer that sits on top of your data source. When you interact with a report (like filtering a chart), Power BI sends live queries back to the original database to get the requested data.

Think of it like getting information for a history report. Import mode is like checking out all the reference books from the library and bringing them home. All the info is at your desk, making it super fast to look things up. DirectQuery is like keeping the books at the library, every time you need a fact, you have to call the librarian to look it up for you.

A Deep Dive into Import Mode

Import mode is the most common and often the default choice for new Power BI users, and for good reason. It offers the best performance and the full range of Power BI capabilities.

How Does Import Mode Work?

When you connect to a data source - like a Google Sheet, a SQL database, or a Shopify export - and choose Import mode, Power BI performs an Extract, Transform, Load (ETL) process. It pulls the data, allows you to clean and model it in the Power Query Editor, and then loads that transformed data into your .PBIX file. This data is refreshed on a schedule you define (e.g., once a day, every four hours).

Advantages of Import Mode

• Blazing-Fast Performance: Because the data is stored in-memory and heavily compressed, interacting with reports is incredibly fast. Slicing, dicing, and filtering visuals happens almost instantaneously, providing a smooth user experience.
• Full DAX Functionality: Data Analysis Expressions (DAX) is the formula language of Power BI. Import mode supports the complete library of DAX functions, giving you unlimited power to create complex calculations and custom metrics.
• Data Source Flexibility: You can effortlessly combine data from various sources. Want to merge a Google Sheet with data from Salesforce and a local Excel file? Import mode handles this seamlessly in the Power Query Editor.
• Less Strain on Source Systems: Since Power BI only hits your source database during a scheduled refresh, it doesn't constantly bombard it with queries, reducing the load on your operational systems.

Disadvantages of Import Mode

• Dataset Size Limitations: The biggest constraint is dataset size. For a Power BI Pro license, the .PBIX file is limited to 1 GB. For Premium licenses, this can go higher, but you are always limited by physical memory. Very large datasets can become unmanageable.
• Data is Not Real-Time: The data is only as fresh as your last refresh. If you need up-to-the-minute data, waiting for the next scheduled refresh (which can be as infrequent as once a day) isn't practical. For a free/Pro license, you are limited to 8 scheduled refreshes per day.
• Initial Load Times: The initial data import and subsequent refreshes can be time-consuming, especially for larger datasets.

When to Use Import Mode:

• You are working with datasets under 1 GB.
• Report performance and a fast user experience are your top priority.
• You need to perform complex DAX calculations.
• You are combining data from multiple different sources (flat files, web sources, databases).
• Your data doesn't need to be updated more than a few times per day (e.g., daily sales summaries, monthly marketing reports).

A Deep Dive into DirectQuery Mode

DirectQuery is built for scenarios where data size or freshness makes the Import model unworkable. It connects directly to the source, ensuring you're always looking at the latest data.

How Does DirectQuery Mode Work?

With DirectQuery, only the data’s schema (the table names and column structures) is saved in your Power BI file. Every interaction in your report - clicking a slicer, opening a new page, filtering a visual - generates a query that Power BI sends to the underlying data source in its native language (like SQL). The source system processes the query and returns the results, which Power BI then displays. Essentially, your database is doing all the heavy lifting.

Advantages of DirectQuery Mode

• Real-Time (or Near Real-Time) Data: This is the headline feature. Because you are querying the source directly, your report always reflects the current state of the data. No refreshes needed.
• Supports Massive Datasets: You are not limited by local memory or .PBIX file sizes. If your data source can handle terabytes of data, DirectQuery allows you to build reports on top of it.
• Handles Data Subject to Rapid Change: Perfect for monitoring operational systems, IoT sensors, or any data source where real-time analysis is critical.

Disadvantages of DirectQuery Mode

• Performance Depends on the Source: Your report's speed is entirely dependent on the performance of the underlying data source. If your database is slow or poorly optimized, your Power BI report will be slow. A complex dashboard can send dozens of queries at once, easily overwhelming an unprepared server.
• DAX Limitations: Many DAX functions are not optimized for translation into source query languages. This means certain calculations and a lot of powerful time-intelligence functions are not available or perform poorly.
• Data Transformation & Modeling Restrictions: The transformations you can perform in the Power Query Editor are more limited. You can’t combine data from multiple sources in a single DirectQuery model (unless using Composite models, which we'll cover next).

When to use DirectQuery:

• Your dataset is far too large to fit into memory (e.g., hundreds of millions or billions of rows).
• The data changes constantly and your reports must reflect these changes in real time.
• You have a powerful, well-optimized data source (like Azure Synapse, Snowflake, or a beefy SQL Server) ready to handle the query load.

"Best of Both Worlds": Live Connections and Composite Models

Beyond the two main modes, you might encounter two other options that extend these concepts.

Live Connection

A Live Connection is similar to DirectQuery but is specific to Analysis Services models (SSAS, an enterprise-level data modeling tool from Microsoft). With a Live Connection, not just the data, but the entire data model - including relationships and measures - lives in the source. You cannot create new measures or relationships in your Power BI desktop file, it’s a purely read-only connection. It is often considered a "flavor" of DirectQuery.

Composite Models

This is where things get really interesting. Power BI allows you to create a Composite Model, which lets you mix and match connection types within the same report. For example, you could have a massive sales fact table using DirectQuery to keep sales data live, while using Import mode for smaller dimension tables like your 'Products' or 'Calendar' tables. This allows you to combine the performance benefits of Import with the real-time capabilities of DirectQuery, offering a flexible and powerful solution for complex scenarios.

Import vs. DirectQuery: A Head-to-Head Comparison

Here’s a quick summary to help you decide:

Import Mode

• Performance: Excellent
• Data Freshness: Stale (Requires Scheduled Refresh)
• Dataset Size: Limited (e.g., 1 GB on Pro)
• DAX Support: Complete
• Data Sources: Can combine all source types
• Source System Load: Low (only during refresh)

DirectQuery Mode

• Performance: Variable (Depends on source)
• Data Freshness: Real-time
• Dataset Size: Virtually unlimited
• DAX Support: Limited
• Data Sources: Typically one at a time
• Source System Load: High (constant querying)

As a best practice, always start with Import mode. If your solution runs into roadblocks because of dataset size or latency requirements, then - and only then - should you explore switching your larger tables to DirectQuery.

Final Thoughts

Choosing between Import and DirectQuery in Power BI is a classic trade-off between performance and data freshness. Import mode offers superior speed and full analytical power for most common business scenarios, while DirectQuery provides a vital solution for real-time analysis on enormous datasets. By understanding these core differences, you can architect reports that are not only insightful but also efficient and perfectly suited to your needs.

While tools like Power BI are incredibly powerful, they still demand a significant learning curve to master concepts like storage modes, DAX, and data modeling. We've seen teams spend hours wrestling with refresh schedules and complex model relationships just to get a clear picture of their business performance. Graphed was created to eliminate this friction entirely. After a one-click connection to your marketing and sales platforms, we believe you should be able to ask questions in plain English - like "Compare my Facebook Ads ROI by campaign this month" - and instantly get a real-time, shareable dashboard, with no steep learning curve required. If you'd rather focus on insights instead of infrastructure, you might enjoy giving Graphed a try.