The SUM Function: Adding Values
The SUM function is an aggregate function that adds up all values in a specific column. You can only use the SUM function with numeric values either integers or decimals.
The AVG Function: Average Your Results
The AVG function works in a similar way as SUM. The difference is that the AVG function adds up or sums up all values and then calculates the average. The average is based on the number of records returned by the SQL statement, so you receive different results based on your WHERE clause.
The COUNT Function: Count the Number of Records Returned
Sometimes, you just want to get a quick count of the number of records returned by a query. You can also use the COUNT function to count the number of records in a table. Suppose you want to know how many orders you have in total. You can use the COUNT function to get a total number of order records.
The MIN and MAX Functions
The MIN and MAX functions find the minimum or maximum value in a recordset. For instance, you might want to find the maximum or highest order total that'* you've had while in business. You might also want to know the minimum or lowest order total value. With these business requirements, you use the MIN and MAX functions.
