rownumber.md

📚 ROW NUMBER

The ROW_NUMBER() function assigns a unique sequential integer to rows within a result set.
It is often used for pagination, ranking, or ordering results uniquely.

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🛠️ Basic Syntax

SELECT column1, 
       ROW_NUMBER() OVER (PARTITION BY column2 ORDER BY column3) AS row_num
FROM table_name;

• PARTITION BY divides the rows into groups (optional).
• ORDER BY determines the sequence of row numbers within each partition.

Example

SELECT employee_id, department_id, 
       ROW_NUMBER() OVER (PARTITION BY department_id ORDER BY salary DESC) AS row_num
FROM employees;

• This query assigns a row number to each employee within their department, ordered by salary.

Key Points

• Each row gets a unique number starting from 1 within its partition.
• If PARTITION BY is omitted, the entire result set is treated as a single group.
• Useful for pagination by selecting ranges of rows.

Additional Example

SELECT order_id, customer_id, 
       ROW_NUMBER() OVER (ORDER BY order_date) AS order_sequence
FROM orders;

• This query numbers all orders by order date, without partitioning.

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🎥 Video Notes

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📝 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?

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DataBase Given

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💻 My SQL Code

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

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🧠 Solution Code / Explanation

SQL COMMAND

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

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