Which of the following is a valid SQL aggregate function?

# Understanding the SQL Aggregate Function SUM()

The SQL aggregate function `SUM()` is an essential concept for anyone working with SQL databases. These aggregate functions perform calculations on a set of values and then return a single value.

Among the options provided in the quiz question, `SUM()` is the valid SQL aggregate function. `COLLECT()`, `COMBINE()`, and `CONNECT()` are not valid SQL aggregate functions as they don't exist in SQL syntax.

The `SUM()` function serves to sum up all the values within a particular column of a table. This can be invaluable when working with large datasets where you need to add all values in a specific row, like calculating the total sales for a business month or determining total working hours.

## Practical Example of SUM()

Let's take a practical example. Suppose you have a Sales table with the following data:

``````Sales_ID | Product_ID | Price
1    |     A      |   10
2    |     B      |   20
3    |     A      |   30
4    |     B      |   40
``````

If you want to find the total Price of all products, you would use the `SUM()` function as follows:

``````SELECT SUM(Price) as Total_Price FROM Sales;
``````

This SQL statement returns the sum of all values under the Price column, which is 100.

## Best Practices for Using SUM()

While `SUM()` is quite straightforward, it's necessary to consider some key points when using it:

1. `SUM()` adds all values in the column, including null values which are considered as zero in this operation.
2. Consider using the `DISTINCT` clause with the `SUM()` function to add only distinct values.
3. If you need to sum values based on certain conditions, incorporate the `WHERE` clause in your SQL statement.

Understanding how to use `SUM()` effectively can help you extract valuable insights from your datasets with ease. It's one of the fundamental tools for data aggregation in SQL, making it a must-learn for working with databases.