Beginning SQL

The results from the query are as follows:
Category Total Cost For Category Members Favorite Category
Thriller 15.98 3
Romance 12.99 2
Horror 18.94 3
War 15.99 4
Sci-fi 15.99 3
Historical 41.97 3
Exercise 2 Solution
All the hard work in creating this query is in the WHERE clause. There are two important conditions for
the WHERE clause: that a town must have two or more members, and that the town must not currently be
listed in the Location table. The WHERE clause is broken down into two subqueries, one nested inside the
other. The outer subquery returns the number of members living in a particular city. The inner subquery
returns all rows from the Location table that match the city name and state:
SELECT City, State FROM MemberDetails MD1
WHERE (SELECT COUNT(*) from MemberDetails MD2
WHERE NOT EXISTS (SELECT * FROM Location L1 WHERE L1.City = MD2.City AND L1.State =
MD2.State)
AND MD1.City = MD2.City AND MD1.State = MD2.State
GROUP BY City, State) >= 2
GROUP BY City, State;
The nested inner subquery is this:
(SELECT * FROM Location AS L1 WHERE L1.City = MD2.City AND L1.State = MD2.State)
If this returns rows, then it means that the city already exists in the Location table, but because you want
only cities not already in that table, use a NOT EXISTS operator in the outer subquery to remove those
cities from the results.
The outer subquery is as follows:
Exercise Answers
(SELECT COUNT(*) from MemberDetails MD2
WHERE NOT EXISTS (SELECT * FROM Location L1 WHERE L1.City = MD2.City AND L1.State =
MD2.State)
AND MD1.City = MD2.City AND MD1.State = MD2.State
GROUP BY City, State)
This SQL returns the number of members living in a city, where the city does not exist in the Location
table. In the main query, you then check to see that this value is 2 or more:
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