SQL LEAD and LAG

Access data from subsequent or previous rows without self-joins.

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The LAG() function accesses data from a previous row, and LEAD() accesses data from a following row. This is essential for calculating period-over-period growth and variance.

Key Takeaways: SQL LEAD and LAG

Mastering SQL LEAD and LAG helps you write clean and reliable SQL code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.

SQL LEAD and LAG Code Example

SQL

SELECT month, revenue,
       LAG(revenue, 1) OVER (ORDER BY month) AS prev_month_rev,
       revenue - LAG(revenue, 1) OVER (ORDER BY month) AS growth
FROM monthly_sales;

Output

Calculates revenue difference compared to previous month

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SQL LEAD and LAG

💡 Key Takeaways: SQL LEAD and LAG

SQL LEAD and LAG Code Example

Key Takeaways: SQL LEAD and LAG