What restrictions apply to use the aggregate function within the select statement Who do nulls affects the aggregate functions?

When using aggregate functions in a SQL SELECT statement, restrictions often include the requirement that any non-aggregated columns in the SELECT list must be included in the GROUP BY clause. Additionally, aggregate functions will ignore NULL values, meaning that NULLs do not contribute to the calculated results, such as averages or counts, which can affect the outcome of the aggregation if NULLs are present. For instance, COUNT will only count non-NULL entries, while SUM will exclude NULLs from its total.