Beginning SQL

Chapter 6
SELECT Category, AVG(DVDPrice)
FROM Films
INNER JOIN Category
ON Films.CategoryId = Category.CategoryId
WHERE AvailableOnDVD = ‘Y’
GROUP BY Category;
The AVG price result receives the alias Average Price, which although not strictly needed, does help
identify what the result means.
Executing this query produces the results in the following table:
Category Average Price
Historical 11.643333
Horror 9.470000
Romance 12.990000
Sci-fi 12.990000
Thriller 7.990000
War 12.990000
MAX() and MIN() in Results
200
The MAX() and MIN() aggregate functions return the lowest and highest values found in a results set,
respectively. Basically, it’s the same as if the results were ordered and the first and last results were
picked from the list. Unlike the SUM() and AVG() functions, you can use MAX() and MIN() with data
types other than numerical data types. For example, you can use MAX() and MIN() to find the earliest
or latest date or time in a date or time field.
The following SQL finds the youngest and oldest members in the MemberDetails table:
SELECT MAX(DateOfBirth), MIN(DateOfBirth)
FROM MemberDetails;
It provides the following results:
MAX(DateOfBirth) MIN(DateOfBirth)
1997-05-28 1937-01-20
In addition to a date or time field, you can also choose a character field. Again, the MIN() and MAX() are
the values for the specified column for the first and last records in an ordered results set. For example,
the following SQL finds the MIN() and MAX() values for the LastName column in the MemberDetails
table where MemberId is less than 3: