Beginning SQL

Appendix A
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
The final query gives the following results:
City State
Townsville Mega State
Chapter 9
Exercise 1 Solution
386
The easiest and safest way to delete data is first to write a SELECT query that selects the data you want
to delete and then to change the SELECT statement to a DELETE statement.
Begin with the SELECT column list and FROM clause:
SELECT StarId, StarName, StarAge FROM FilmStars S1;
This query simply returns all rows and columns from the table. The table has a primary key and the
StarId column, and luckily enough, the values entered there are unique. However, the star’s name
should be unique, but it isn’t. Therefore, you need to search for instances where there are duplicate
names but where the StarId is different. To do this, you can use an IN operator and a subquery that simply
returns all rows:
SELECT StarId, StarName, StarAge FROM FilmStars S1
WHERE StarName IN (SELECT StarName FROM FilmStars);
If you run this query, you get the following results:
StarId StarName StarAge
1 Boris Carlot 102
1 Scarlet O’Hairpin 89
3 Boris Carlot 102
4 Michael Hourglass 56
5 Dusty Hoffperson 48
6 Boris Carlot 102
7 Dusty Hoffperson 48