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Learn Advanced Window Function Patterns | Window Functions for Trends and Rankings
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SQL for Business Intelligence Analysts

bookAdvanced Window Function Patterns

As you move deeper into business intelligence analytics, advanced window function patterns like LAG(), LEAD(), and PERCENT_RANK() allow you to uncover trends, compare periods, and evaluate performance in new ways. These functions help you go beyond simple aggregations and rankings, offering richer insights into your business data.

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SELECT d.date, s.amount AS sales, LAG(s.amount) OVER (ORDER BY d.date) AS previous_sales FROM sales s JOIN dates d ON s.sale_date_id = d.date_id ORDER BY d.date;
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By using the LAG() function, you can compare each day's sales to the previous day's sales. This lets you analyze trends such as whether sales are increasing, decreasing, or remaining steady over time. For example, you might quickly spot a drop in sales on a particular date, prompting further investigation into possible causes.

Note
Definition

The LAG() and LEAD() window functions let you access data from previous or following rows within the result set. LAG() retrieves a value from a preceding row, while LEAD() retrieves from a following row. These are powerful tools for trend analysis, such as comparing current and previous values or forecasting.

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SELECT ep.employee_id, ep.sales_achieved AS sales, PERCENT_RANK() OVER (ORDER BY ep.sales_achieved) AS percentile FROM employee_performance ep;
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Using PERCENT_RANK() helps you evaluate employee performance by showing each employee's relative standing among their peers. A percentile rank close to 1 means the employee is among the top performers, while a value near 0 indicates a lower rank. This can be useful for identifying high achievers or employees who may need additional support.

You can combine multiple window functions in a single query to build comprehensive business reports. For instance, using both LAG() and PERCENT_RANK() together allows you to see not only how an employee's performance compares to others, but also how it has changed over time. This approach provides a more complete view of trends and rankings, supporting better decision-making.

1. What does the LAG() function do in SQL?

2. How can percentiles help in employee performance analysis?

3. Give an example of using LEAD() in a business scenario.

question mark

What does the LAG() function do in SQL?

Select the correct answer

question mark

How can percentiles help in employee performance analysis?

Select the correct answer

question mark

Give an example of using LEAD() in a business scenario.

Select the correct answer

Everything was clear?

How can we improve it?

Thanks for your feedback!

SectionΒ 3. ChapterΒ 5

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bookAdvanced Window Function Patterns

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As you move deeper into business intelligence analytics, advanced window function patterns like LAG(), LEAD(), and PERCENT_RANK() allow you to uncover trends, compare periods, and evaluate performance in new ways. These functions help you go beyond simple aggregations and rankings, offering richer insights into your business data.

123456789
SELECT d.date, s.amount AS sales, LAG(s.amount) OVER (ORDER BY d.date) AS previous_sales FROM sales s JOIN dates d ON s.sale_date_id = d.date_id ORDER BY d.date;
copy

By using the LAG() function, you can compare each day's sales to the previous day's sales. This lets you analyze trends such as whether sales are increasing, decreasing, or remaining steady over time. For example, you might quickly spot a drop in sales on a particular date, prompting further investigation into possible causes.

Note
Definition

The LAG() and LEAD() window functions let you access data from previous or following rows within the result set. LAG() retrieves a value from a preceding row, while LEAD() retrieves from a following row. These are powerful tools for trend analysis, such as comparing current and previous values or forecasting.

123456
SELECT ep.employee_id, ep.sales_achieved AS sales, PERCENT_RANK() OVER (ORDER BY ep.sales_achieved) AS percentile FROM employee_performance ep;
copy

Using PERCENT_RANK() helps you evaluate employee performance by showing each employee's relative standing among their peers. A percentile rank close to 1 means the employee is among the top performers, while a value near 0 indicates a lower rank. This can be useful for identifying high achievers or employees who may need additional support.

You can combine multiple window functions in a single query to build comprehensive business reports. For instance, using both LAG() and PERCENT_RANK() together allows you to see not only how an employee's performance compares to others, but also how it has changed over time. This approach provides a more complete view of trends and rankings, supporting better decision-making.

1. What does the LAG() function do in SQL?

2. How can percentiles help in employee performance analysis?

3. Give an example of using LEAD() in a business scenario.

question mark

What does the LAG() function do in SQL?

Select the correct answer

question mark

How can percentiles help in employee performance analysis?

Select the correct answer

question mark

Give an example of using LEAD() in a business scenario.

Select the correct answer

Everything was clear?

How can we improve it?

Thanks for your feedback!

SectionΒ 3. ChapterΒ 5
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