Beginning SQL

Chapter 6
Try It Out Selecting Data with MAX() and MIN()
1. The film club chairperson wants to know the dates of birth of the youngest and oldest members
in each state. Use the following SQL:
SELECT State, MAX(DateOfBirth), MIN(DateOfBirth)
FROM MemberDetails
WHERE State IS NOT NULL
GROUP BY State;
How It Works
This query is a little easier than the other examples because all the data comes from the same table; there
is no need for joins. The SELECT statement lists the columns and expressions that form the final results:
SELECT State, MAX(DateOfBirth), MIN(DateOfBirth)
The FROM part is easy: everything comes from the MemberDetails table. However, some values in the
State and DateOfBirth columns are NULL, so you use an IS NOT NULL operator in the WHERE clause to
exclude them:
FROM MemberDetails
WHERE State IS NOT NULL
Finally, you want results grouped based on the State column, so you add a GROUP BY clause:
GROUP BY State
Although it’s true that all columns listed in the SELECT statement must also appear in the GROUP BY
clause, it’s not true of aggregate functions like MAX() and MIN(), so they don’t appear in the GROUP BY
clause. Executing the entire statement produces the following results set:
State MAX(DateOfBirth) MIN(DateOfBirth)
Golden State 1997-05-28 1956-08-07
Mega State 1994-05-28 1937-01-20
New State 1992-07-17 1952-10-05
So far, you’ve learned how to group and summarize results with aggregation functions. The next section
explains how to use the HAVING clause to limit which groups are displayed and how to use the HAVING
clause with the aggregation functions.
Using the HAVING Clause with
GROUP BY Statements
202
The HAVING clause enables you to specify conditions that filter which group results appear in the final
results. In some ways, the HAVING clause resembles a WHERE clause for groups, in that you place it