Basic Statistics in SQL: Average, Median, Percentiles and Standard Deviation
Calculate averages, medians, percentiles, mode and standard deviation in SQL Server and MySQL, find outliers, and learn which number to report.
Window Functions
Top N per Group in SQL Server: Get the Latest Record for Each Group
How to get the latest record or the top N rows for each group in SQL Server with ROW_NUMBER(), handle ties correctly, and when CROSS APPLY or WITH TIES is the better choice.
Running Totals in SQL Server: Cumulative Sums and Running Balances
How to calculate a running total and a running account balance in SQL Server with SUM() OVER, reset it per month or account, and avoid the two mistakes that give wrong or slow results.
SQL Window Functions Explained Simply (ROW_NUMBER, RANK, LAG and More)
A beginner-friendly guide to SQL window functions: OVER, PARTITION BY, ROW_NUMBER, RANK, running totals and LAG, with clear examples.