Calculating the Average Hourly Pay Rate in SQL

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As a self-learner of SQL, you may have encountered situations where you need to calculate the average hourly pay rate for employees. In this article, we will explore how to achieve this using various SQL techniques.

Understanding the Problem

The provided SSRS report query retrieves data from the RPT_EMPLOYEECENSUS_ASOF table in the LAWSONDWHR database. The query filters the data based on several conditions and joins with another table (not shown) to retrieve specific columns, including HourlyPayRate. However, the question at hand is how to calculate the average hourly pay rate for each employee.

Solution 1: Using GROUP BY

The solution provided in the Stack Overflow answer involves using the GROUP BY clause. This approach is straightforward and effective for calculating the average value of a column across all rows for a given group.

SELECT Employee, AVG(HourlyPayRate) AS AvgHourlyRate
FROM (
    SELECT Employee, CASE 
           WHEN HRPERIOD = 3 THEN 'March'
           WHEN HRPERIOD = 6 THEN 'June'
           WHEN HRPERIOD = 9 THEN 'September'
           WHEN HRPERIOD = 12 THEN 'DECEMBER'
       END HRPERIOD,
       EMPLOYEE,
       HRYEAR,
       PAY_RATE,
       FTE_TOTAL,
       JOB_CLASS_NAME,
       JOB_CLASS,
       SALARY_CLASS,
       CASE
           WHEN SALARY_CLASS = 'S'
                OR PAY_RATE > 1000 THEN (PAY_RATE / 2080)
           ELSE PAY_RATE
       END AS HourlyPayRate
    FROM [LAWSONDWHR].[dbo].[RPT_EMPLOYEECENSUS_ASOF]
    WHERE PROCESS_LEVEL = @PROCLEVEL
      AND HRYEAR = @HRYEAR
      AND HRPERIOD = @HRPERIOD
      AND JOB_CLASS = 'RN'
      AND FTE_TOTAL != 0
      AND MASTER_EMP_STATUS NOT IN ('ZZ', 'T1')
) a
GROUP BY Employee

In this query, we first select the required columns from the RPT_EMPLOYEECENSUS_ASOF table. We then use a subquery to calculate the average value of the HourlyPayRate column for each employee.

Understanding GROUP BY Clauses

A GROUP BY clause is used in SQL to group rows that have the same values in one or more columns. When you apply an aggregate function like AVG(), SUM(), or MAX(), the database will calculate the value for each group and return a single result.

In this case, we use GROUP BY Employee to group the results by employee name, which allows us to calculate the average hourly pay rate for each individual.

Solution 2: Using Window Functions (SQL Server 2012 and Later)

If you are using SQL Server 2012 or later, you can use window functions like AVG() with the OVER clause to achieve a similar result. This approach is useful when you need to perform calculations on a subset of rows within a result set.

SELECT Employee, AVG(HourlyPayRate) OVER (PARTITION BY Employee) AS AvgHourlyRate
FROM (
    SELECT Employee, CASE 
           WHEN HRPERIOD = 3 THEN 'March'
           WHEN HRPERIOD = 6 THEN 'June'
           WHEN HRPERIOD = 9 THEN 'September'
           WHEN HRPERIOD = 12 THEN 'DECEMBER'
       END HRPERIOD,
       EMPLOYEE,
       HRYEAR,
       PAY_RATE,
       FTE_TOTAL,
       JOB_CLASS_NAME,
       JOB_CLASS,
       SALARY_CLASS,
       CASE
           WHEN SALARY_CLASS = 'S'
                OR PAY_RATE > 1000 THEN (PAY_RATE / 2080)
           ELSE PAY_RATE
       END AS HourlyPayRate
    FROM [LAWSONDWHR].[dbo].[RPT_EMPLOYEECENSUS_ASOF]
    WHERE PROCESS_LEVEL = @PROCLEVEL
      AND HRYEAR = @HRYEAR
      AND HRPERIOD = @HRPERIOD
      AND JOB_CLASS = 'RN'
      AND FTE_TOTAL != 0
      AND MASTER_EMP_STATUS NOT IN ('ZZ', 'T1')
) a

In this query, we use the AVG() window function with the PARTITION BY clause to calculate the average hourly pay rate for each employee. The PARTITION BY clause specifies that we want to calculate the average value for each group of rows based on the Employee column.

Understanding Window Functions

Window functions in SQL allow you to perform calculations on a subset of rows within a result set. They provide additional information about the current row, such as the total or running sum of values.

In this case, we use the AVG() window function with the PARTITION BY clause to calculate the average hourly pay rate for each employee. This approach can be more flexible and powerful than using a subquery with GROUP BY.

Conclusion

Calculating the average hourly pay rate for employees is a common requirement in various industries, especially when working with payroll data. In this article, we explored two approaches to achieve this using SQL: grouping rows by employee name and using window functions.

Both approaches have their strengths and weaknesses, depending on your specific use case and database management system. By understanding how to apply these techniques effectively, you can streamline your data analysis and reporting processes.

Last modified on 2024-08-26