SQL JOINs without double counting
Find out why joining an invoice to its lines can accidentally inflate totals, and how to check the result.
Learn by doing
Practical SQL and data analytics guides
Short, useful explanations with working examples. Start with a question you might face at work, see how to answer it and then try the technique in Insyt's free practice tools.
SQL guides
GROUP BY and HAVING
Build totals by group, filter aggregate results and understand when to use WHERE instead.
Analytics at work
How to calculate KPI variance
Compare actuals against a target and explain the difference between percentages and percentage points.
Mean vs median: worked example
Compare two averages and see why an unusual value changes the mean more than the median.
Starting a career in analytics
How to become a data analyst
See the skills, everyday tasks and practical first project that build useful evidence of capability.
Prefer to start with practice?
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