Скачать или смотреть SQL Window Functions Part 2: LEAD, LAG, FIRST_VALUE, LAST_VALUE, NTH_VALUE Explained #16

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SQL Window Functions Tutorial (Part 2): LEAD, LAG, FIRST_VALUE, LAST_VALUE, NTH_VALUE

In this follow-up video on SQL window functions, I focus on value-based functions that help you compare values across rows in a partition. Using a real-world example from my local MySQL Workbench database (sql_practice), I demonstrate how each function works and how it changes the result set.

What’s Covered in This Video:

✅ Window Functions Covered:
• LEAD()
• LAG()
• FIRST_VALUE()
• LAST_VALUE()
• NTH_VALUE()


1. Link for Installing MySQL on a Mac:

   • How to install Mysql on a Mac- M1/M2/M3 [2...  

2. Youtube Link for downloading database and importing it on your local computer:

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In this video, I introduce SQL Window Functions and focus on the ranking-based functions, demonstrating their application through a real-world example from my MySQL Workbench database (sql_practice with an employees table).


Timestamps:
0:00 Intro
00:14 What are value-based window functions?
00:44 What is LAG window function
01:34 Example for LAG window function
03:55 What is LEAD window function
04:06 Example for LEAD window function
04:44 What is FIRST_VALUE window function
04:55 Example for FIRST_VALUE window function
05:33 What is LAST_VALUE window function
06:03 Example for LAST_VALUE window function
06:58 What is NTH_VALUE window function
07:17 Example for NTH_VALUE window function

📊 Demonstration Highlights:
• Partition employees by department.
• Sort salaries in descending order within each department.
• Apply all five value-based functions on the salary column.
• Show how each function returns different insights by looking ahead, behind, or within a partition.

🎓 What You’ll Learn:
• When to use each value-based window function.
• How to compare current row values with other rows in the same group.
• The impact of ordering and partitioning on window function results.


Who Is This Video For?
• SQL learners progressing beyond basic SELECT queries.
• Data analysts working with MySQL or analytics queries.
• Anyone preparing for SQL interviews or aiming to master window functions.


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