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SQL is the foundation of data manipulation and retrieval in data engineering, and knowing SQL is essential for passing your data engineering interviews. This blog discusses the most critical SQL principles to know, with an emphasis on those that are frequently evaluated in interviews.
SQL’s aggregate functions enable you to execute computations on a set of values and produce a single result. These are critical for summarizing data, particularly when dealing with huge datasets.
Common Aggregate Functions:AVG(): Returns the average value of a numeric column.COUNT(): Counts the number of rows (or distinct values) in a dataset.SUM(): Returns the sum of a numeric column.MIN(): Returns the smallest value in a column.MAX(): Returns the largest value in a column.
Example:
SELECT department, AVG(salary) AS average_salary, MIN(salary) AS lowest_salary
FROM employees
GROUP BY department;
Aggregate functions are essential for any data engineer who wants to summarize or process data…