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Julien Le MercierJL

Julien Le Mercier

Senior Power BI Consultant | Modeling & DAX

€600/day
Paris, FR
8-15 years

Average response time: 1 hour

Freelancer profile translated to English.
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About Julien

Senior Power BI Consultant, Microsoft PL-300 certified, 10+ years in large accounts (Dior, VINCI Airports, Tarkett, BPCE, FDJ, Orange). I support business departments and data teams in the creation, redesign, and industrialization of their Power BI reporting.

My expertise covers business modeling (facts/dimensions, star schema), DAX and Power Query performance optimization, KPI reliability, Power BI Service governance, data quality, and data visualization.

I work in demanding large account environments, including: building reusable BI foundations, redesigning existing models on millions of rows, migrating legacy reporting (BO, SAS, Excel) to Power BI, optimizing DAX/Power Query, implementing Dataflows, deployment pipelines, Power Platform applications (Power BI + Power Apps), and supporting business users.

References: Dior (multi-domain industrial BI, 20+ reports), VINCI Airports (redesign of an international portfolio of 12 reports / 70 airports / 13 countries), Tarkett (model redesign + diffusion industrialization), BPCE, FDJ, Orange.

My typical assignments:
· Redesign of slow or unreliable Power BI reports
· Migration of BO / SAS / Excel to Power BI
· Reliability of KPIs and business calculation rules
· Fact/dimension modeling and model optimization
· DataViz and user experience improvement
· Power BI governance, deployment, and adoption

Objective: build reliable, fast, maintainable reports that are actually used by the business.
  • French

    Native or bilingual

  • English

    Fluent

Can work on-site
Paris (up to 20km), Rennes (up to 50km), Nantes (up to 20km)

Experience

  • Christian DIOR
    Senior Power BI Consultant — Industrial BI & Cross-functional Steering
    LUXURY GOODS
    September 2024 - Today (1 year and 9 months)
    Paris, France
    For Christian Dior Couture, I am supporting the industrial division in structuring a cross-functional Power BI BI foundation to steer production, purchasing, logistics, quality, and collection development activities.

    The mission combines data architecture, M3 ERP business modeling, Power BI Dataflows, business reporting creation, repository reliability, and automated alerting setup.

    The objective is to strengthen confidence in industrial indicators, improve the readability of operational steering, and make data reusable across several business domains.

    • Industrial Power BI Dataflows Cube
    • Fact/dimension modeling on M3 ERP data
    • Production, purchasing, quality, logistics reporting
    • Data quality controls and anomaly detection
    • Automated email alerting
    • Performance optimization and model maintainability
    Microsoft Power BI Figma Power BI DAX Dataflow Data Modeling
  • Tarkett
    Power BI Redesign — Reliable KPIs, Performant Reports & Industrialized Distribution
    CIVIL ENGINEERING
    February 2024 - June 2024 (4 months)
    Puteaux, France
    Tarkett had an existing Power BI environment with inconsistent KPIs and performance limitations.
    My mission within the Global Innovation Team consisted of taking over the existing setup, identifying the causes of discrepancies, rebuilding a more robust data model, and industrializing report distribution.

    What I did:
    • KPI audit and analysis of result discrepancies.
    • Redesign of the Power BI model to improve reliability and maintainability.
    • Migration of the data source from Excel to Power Apps.
    • Validation of indicators with business teams.
    • Visual redesign of reports in Figma.
    • Implementation of a deployment pipeline.
    • Creation of a Power BI application with audience management.
    • Technical and functional documentation.
    Benefits for the client:
    • Consistent and validated KPIs.
    • More reliable data model.
    • More readable reports.
    • Better-controlled deployment cycle.
    • Distribution adapted to different business audiences.
    Project Management Microsoft Power BI DAX Studio Data Model Figma
  • Vinci Airports
    Power BI Optimization — Performance, Data Model & DataViz
    AVIATION AND AEROSPACE
    May 2023 - January 2024 (8 months)
    Nanterre, France
    VINCI Airports had a portfolio of about a dozen Power BI reports covering an international scope of 70 airports in 13 countries.
    My mission was to overhaul the existing setup to improve performance, simplify the data model, reduce DAX complexity, and modernize the user experience.

    What I did:
    • Redesign of the data model for 12 Power BI reports.
    • Performance optimization on several million rows.
    • Removal of complex DAX measures based on SWITCH.
    • Moving part of the time logic to Power Query.
    • Implementation of Field Parameters to rationalize analyses.
    • Creation of Figma templates to standardize reports.
    • Complete visual redesign of the report portfolio.
    • Creation of an environment report connected to GCP.
    • Definition of Scope 1, 2, and 3 KPIs with business teams.
    • Creation of a report dedicated to airlines.

    Benefits for the client:
    • Improved navigation and refresh times.
    • Simpler models to maintain.
    • Streamlined and more readable DAX.
    • Standardized report portfolio.
    • Better adoption thanks to a clearer visual experience.
    • Business reporting adapted to an international context.
    Microsoft Power BI DAX Studio Google Cloud Figma Graphic Design

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Education

  • Programme - Membre de la conférence des grandes écoles, Master of Science (MSc) Data Management
    PSB Paris School of Business
    2018
    Programme - Membre de la conférence des grandes écoles, Master of Science (MSc) Data Management
  • Professional Bachelor's Degree in Data Mining
    IUT Paris Descartes
    2016
    Licence Professionnelle Data Mining

Skill set

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