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OpenSAFELY documentation
How-to guides
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    GitHub
    GitHub
    • Introduction
      • Our philosophy
      • Security
      • Safe data access: The Five Safes
      • Access policies
      • Technical architecture
      • Type One Opt Outs
      • Contributing
    • Getting started
      • Tutorial
        • Introduction
        • Create a GitHub account
        • Create a GitHub repository
        • Create a GitHub codespace
        • Generate a first dataset
        • Update the dataset definition
        • Run the project pipeline
        • Add a scripted action to the pipeline
        • Publish the changes to GitHub
        • Check the automated tests pass
        • Delete the GitHub codespace
        • See the next steps
      • How-to guides
        • How to add GitHub Codespaces to your project
        • How to update GitHub Codespaces in your project
        • How to use GitHub Codespaces in your project
        • How to use released outputs in GitHub Codespaces
        • How to troubleshoot common issues in GitHub Codespaces
        • How to use Git effectively
        • How to use the OpenSAFELY command-line interface
        • How to create a code repository for your project
      • Explanation
        • Options for running OpenSAFELY
        • Understanding GitHub Codespaces
        • Understanding the software used to run OpenSAFELY
      • Analysis workflow
      • Federated analytics
      • GitHub repositories
        • Introduction to codelists
        • Building a codelist
        • Adding codelists to a project
        • Keeping codelists up to date
        • Overview
        • The project pipeline
        • Scripted actions
        • Reusable actions
      • Jobs site
      • Level 4 server
      • Viewing and releasing outputs
        • Viewing outputs with Airlock
        • Releasing research outputs from the Level 4 server
        • Applying statistical disclosure control
        • Requesting release of research outputs
        • Review process for release requests
        • Viewing released outputs
        • Viewing and Releasing with Airlock
          • How-to guides
            • How to access and log in Airlock
              • View output files in a workspace
              • Create and submit a release request
              • Respond to a returned request
              • Edit a file on a request
              • Withdraw a request
              • Review a request
              • Release files
          • Explanation
            • Why Airlock?
            • How does a workspace file differ from a request file?
            • Workflow and permissions
            • Notifications
          • Reference
            • Terms and definitions
            • File icons and colours
            • Alternative ways to view files
            • Viewing underlying source code
            • Downloading files
            • Request state diagram
        • Overview
        • Create a draft
        • Review process
        • Publishing a report
        • Telling us about changes to your project
        • Project completion
      • Adding your pre-print/paper to OpenSAFELY.org
      • Information for system integrators
          • Overview
          • Working with dates
          • Working with codelists
          • Dummy data and expectations
          • Variable reference
          • Measures
          • Create inclusion/exclusion flowcharts
          • Programming tricks
      • Developing a protocol
      • Using Git effectively
      • Code reviews
      • Case-control studies
      • Writing performant code
    • ehrQL
      • Tutorial
        • Setting up
        • Working with tables
        • Writing a dataset definition
        • Generating a dummy dataset
        • Committing the dataset definition
        • Writing a more complex dataset definition
        • Pushing the commits to GitHub
        • Tidying up
      • How-to guides
        • Using ehrQL to answer specific questions
        • How to include and exclude patients from your study population
        • Resolving ehrQL errors
        • How to use dummy data in an ehrQL dataset definition
        • How to use dummy data in an ehrQL measures definition
        • How to assign multiple columns to a dataset programmatically
        • How to work with codelists
        • How to test your dataset definition
      • Reference
        • Language reference
        • Language features
        • Backends
        • Table schemas
        • Command line interface
        • Upgrading ehrQL from v0 to v1
      • Explanation
        • ehrQL backend tables
        • ehrQL output formats
        • Using ehrQL in OpenSAFELY projects
        • Running ehrQL
        • Using the measures framework
        • Selecting populations for study
    • Data sources
      • Overview
      • SystmOne primary care
      • EMIS primary care
      • Covid-19 test results
      • Covid-19 therapeutics
      • Emergency attendances
      • High Cost Drugs
      • Hospital admissions
      • In-hospital deaths (covid-19 only)
      • Intensive care admissions (covid-19 only)
      • International Severe Acute Respiratory and emerging Infection Consortium
      • Registered deaths
      • UK Renal Registry
      • How to get help
      • OpenSAFELY co-piloting service
      • Requesting new libraries
      • Plan S and OpenSAFELY
      • Updating the documentation
    • Bennett Institute Open Manifesto
    • Platform News

    How-to guides

    The how-to guides provide practical steps for working with ehrQL in your project.

    • Using ehrQL to answer specific questions
    • How to include and exclude patients from your study population
    • Resolving ehrQL errors
    • How to use dummy data in an ehrQL dataset definition
    • How to use dummy data in an ehrQL measures definition
    • How to assign multiple columns to a dataset programmatically
    • How to work with codelists
    • How to test your dataset definition
    Previous
    Tidying up
    Next
    Using ehrQL to answer specific questions
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