-- senior database administrator & bi consultant
Ronald de Groot
SQL Server runs better once I've had a look at it.
Senior (Azure) SQL Server DBA and SSIS/ETL/BI consultant with over 30 years of experience. Specialised in performance tuning, execution plans, indexes and migrations to Azure.
Complex database problems, analysed fast
Since 1992 I have worked as a freelance DBA and BI consultant for banks, insurers, healthcare organisations, energy companies and industry. I analyse complex problems quickly and enjoy coming up with technical solutions — fast. On a project I'm the one who gets things moving: careful planning means I hit deadlines.
New technologies challenge me; I want to understand them quickly and thoroughly. At Stichting BKR (the Dutch national credit registry) I spent years migrating failover cluster environments to Azure SQL Database — and my IT colleagues voted me winner of the "Bruggenbouwer" (bridge builder) trophy for that Azure migration work.
My heart is in performance tuning: reading execution plans, designing the right indexes and turning a slow query into a fast one. I've also built ETL solutions with SSIS and Azure Data Factory, data warehouses and cubes (SSAS) for many years.
Beyond that I'm calm, stress-resistant and helpful — a genuine finisher who doesn't shy away from problems. Outside work you'll find me on a road bike or mountain bike, or outdoors flying a drone.
What I'm good at
From database administration and T-SQL to ETL pipelines and BI — this is my toolbox.
Certifications & recognition
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AZURE
Microsoft Certified: Azure Database Administrator
Certified since October 2020 (DP-300).
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AWARD
BKR "Bruggenbouwer" trophy
Voted by all IT colleagues for supporting the various Azure migrations.
Over 30 years in the field
A selection of recent assignments. The full list goes back to 1992.
Heemskerk, FMgroup · SQL Server DBA
Data migrations.
BMN · SQL Server DBA
Performance tuning of the ETL load process.
NEP · ETL Consultant
Maintaining and implementing ETL changes in SSIS.
Stichting BKR · Azure SQL Server DBA
Migration of databases from failover cluster environments (incl. CKI3, VIS, EVA, VPS, KYC) to Azure SQL Database. Supporting scrum teams, Azure Cost & Security Management, Azure Stack HCI data sync and the Ola Hallengren maintenance solution.
EMS / ABN AMRO · DBA / BI Developer
Performance tuning and redesign of databases and ETL for loading credit card transactions; central export functionality and cube changes.
Greenchoice & WMD · DBA
Setting up remote DBA services; security reporting with the SQL Server Vulnerability Assessment for all database servers in the domain.
Menzis · DBA / BI Developer
Performance tuning, SQL Audit implementation for GDPR compliance and ETL development for SAS.
WMD, Bartimeus & Marel · DBA / BI Developer
VLDB data warehouse for sensor measurements (Big Data), enterprise data warehouse sourced from SAP and Microsoft Dynamics, data warehouse with a QlikView frontend and Azure ETL.
Propertize, Smurfit Kappa, SNS Reaal & PGGM · DBA / BI Developer
Database migrations, a generic SOX audit implementation (DBSP Policy), conversions and ETL for the Actuarial Database (coverage ratio reporting, annual accounts).
1992 — 2011 · DBA/BI work for clients including:
From the trenches: execution plans & indexes
Practical articles about the topics I work with every day.
Statistics Parser
Paste your STATISTICS IO/TIME output and get clear signals instantly — physical reads, worktables, skewed CPU/elapsed time. Free, 100% in your browser, with an optional full report by email.
Try the tool → -- parameter sniffing · PSP · newParameter Sensitive Plans (PSP) versus Parameter Sniffing
SQL Server 2022's Parameter Sensitive Plans route skewed parameter values to their own cached plan variant instead of forcing one plan to fit all — demonstrated on the classic Posts.ParentId cardinality problem.
Read on dbaronald.nl → -- string functions · execution plansExecution Plans of all String Functions
Thirty-three T-SQL string functions tested one by one against StackOverflow2010, each with its own execution plan — from ASCII to UPPER.
Read on dbaronald.nl → -- table variables · temp tablesTable Variables versus #Temp Tables
Table variables have no statistics? A common assumption — but on recent SQL Server versions, indexed table variables can carry real statistics too, visible right in the execution plan.
Read on dbaronald.nl → -- partitioning · index maintenanceYou Want to Partition Your Huge Table.. Ok Fine.. Let's Go.
How to partition a huge existing table using only metadata-only SWITCH operations and index seeks — no size-of-data operation required.
Read on dbaronald.nl → -- join order · execution plansWhy Join Order Can Make or Break Your Query Performance
Seven variations of one query on StackOverflow2013 show how picking the wrong build/outer side wastes most of the runtime — hints included.
Read on dbaronald.nl → -- query plan · aiAI and Where Does Query Time Go? Using Claude's Query Plan Analysis Skill
A scalar function hides where query time goes. Claude's plan-analysis skill flags it — inlining with STRING_AGG and one index fix it.
Read on dbaronald.nl → -- query store · aiAutomate Executionplan Analysis by Skill and Query Store
Execution plans from Query Store, analyzed automatically by Erik Darling's execution plan skill for Claude Code — performance recommendations included. (In Dutch)
Read on dbaronald.nl → -- ai · query tuningIs AI making an end to my job as a SQL Server query tuner?
Claude reads an execution plan and recommends the index that takes a query from 73 seconds to 435 ms. What's left for the human tuner?
Read on dbaronald.nl → -- query processing · seriesRereading Craig Freedman: ten parts of query processing
Freedman's classic blog (2006–2010) re-tested on modern SQL Server, with real execution plans. The reading guide to all ten parts.
Read article → -- index maintenance · updatedIndexOptimize and additions to Ola Hallengren's dbo.CommandLog
Extra columns that pull page count, fragmentation, size and duration straight out of the ExtendedInfo XML in dbo.CommandLog.
Read on dbaronald.nl → -- performance tuningReading execution plans: what to check first?
An execution plan can be overwhelming. With these five checks you'll find the culprit in most plans within minutes.
Read article → -- indexesIndex tuning: clustered, nonclustered and included columns
The right index is the difference between milliseconds and minutes. How to choose column order and when INCLUDE pays off.
Read article → -- all articlesMore SQL tips
Browse the full list of articles about SQL Server, performance and Azure.
To the overview →Recent projects on GitHub
From server room to cockpit
When I'm not tuning queries, I fly my own plane — the PH-3B7, a Tecnam P96 Golf. And once a developer, always a developer: I built my own flight tools in C#, AI-assisted with Claude Code.
NavigationPlan
A simple but very handy tool for creating a VFR navigation plan: legs, headings, times and fuel — ready for the kneeboard.
View on GitHub → -- C# · open source
WeightBalance
Weight & balance calculator for the Sonaca (Sling 2): enter fuel, crew and baggage and see instantly whether you're inside the envelope.
View on GitHub →A slow query, or a migration that has to succeed?
Happy to help — from a second opinion on an execution plan to full Azure SQL migrations and remote DBA services via OpenData.nl.