Data Engineering Associate with Databricks Practice Exam

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What does the SQL function COUNT(*) return?

Only non-NULL values
Only rows with matching criteria
The total number of rows in a table, including NULLs
The count of unique rows

The correct answer is: The total number of rows in a table, including NULLs

The SQL function COUNT(*) is designed to return the total number of rows in a specified dataset or table, and it includes all rows regardless of whether they contain NULL values. This comprehensive counting is particularly useful when you want an overview of how many records exist in a table, without filtering or considering the content of those records. When using COUNT(*), every row in the table contributes to the total, including those containing NULLs in one or more columns. This makes it distinct from other functions that may operate on specific columns and only count non-NULL values or unique instances. Thus, it provides a complete picture of the table’s row count, which is integral for various data analysis and reporting tasks.