SQL for Data Analysis: Advanced Techniques

In the previous articles, we have covered a wide range of SQL topics. Now, let’s focus on advanced SQL techniques specifically for data analysis. This includes:

• Window Functions for Advanced Analytics
• Common Table Expressions (CTEs) for Complex Queries
• Advanced Aggregation Techniques
• Time Series Analysis
• Using SQL for Statistical Analysis
• Data Cleaning with SQL

1. Window Functions for Advanced Analytics

Window functions allow you to perform calculations across a set of table rows related to the current row. They are incredibly useful for running totals, moving averages, and ranking.

Running Total Example:

To calculate the running total of sales:

SELECT 
    product, 
    sale_date, 
    sale_amount, 
    SUM(sale_amount) OVER (ORDER BY sale_date) AS running_total
FROM sales;

Moving Average Example:

To calculate a 3-month moving average of sales:

SELECT 
    product, 
    sale_date, 
    sale_amount, 
    AVG(sale_amount) OVER (ORDER BY sale_date ROWS BETWEEN 2 PRECEDING AND CURRENT ROW)…