de_notes

📚 LEAD

The LEAD() function is used in SQL to access data from the next row in the result set, without using a self-join.
It is helpful for comparing a row to the row that follows it.

---

🛠️ Basic Syntax

SELECT column1, 
       LEAD(column2, offset, default_value) OVER (PARTITION BY column3 ORDER BY column4) AS next_value
FROM table_name;

• column2 is the column to look ahead.
• offset (optional) specifies how many rows forward to look (default is 1).
• default_value (optional) is returned if there is no next row.

Example

SELECT employee_id, salary,
       LEAD(salary, 1) OVER (ORDER BY salary DESC) AS next_highest_salary
FROM employees;

• This query shows each employee’s salary and the salary of the next highest-paid employee.

Key Points

• LEAD() is often used for gap analysis, trend comparisons, or sequential reporting.
• If there is no next row, it returns NULL unless a default value is specified.
• Works great in combination with PARTITION BY for grouped data.

Additional Example

SELECT order_id, order_date,
       LEAD(order_date, 1) OVER (PARTITION BY customer_id ORDER BY order_date) AS next_order_date
FROM orders;

• This query shows each customer's next order date based on their current order.

---

🎥 Video Notes

---

📝 Problem Description

Describe the problem, challenge, or topic discussed in a video related to SELECT FROM.
What concept was explained or what exercise was solved?

---

DataBase Given

---

💻 My SQL Code

-- Write your SQL code attempt or solution related to SQL COMMAND
SQL COMMAND

---

🧠 Solution Code / Explanation

SQL COMMAND

Explanation - Explain what you learned, any key takeaways, or how you solved the problem related to COMMAND._

---

⬅️ Previous: RANK Next ➡️ WITH STATEMENTS