oracle | Page 7

8
18 Spalding Medical Inc. 8
19 Kendall-Taylor Corp. 8
20 Malden Labs 8
21 Crimson Medical Inc. 9
22 Nichols Industries 9
23 Owens-Baxter Corp. 9
24 Jackson Medical Inc. 9
25 Worcester Technologies 9
26 Alpha Technologies 10
27 Phillips Labs 10
28 Jaztech Corp. 10
29 Madden-Taylor Inc. 10
30 Wallace Industries 10
Since we neglected to impose any conditions via a WHERE clause, our query returns
every row from the customer table.If we want to restrict the set of data returned by
the query, we could include a WHERE clause with a single condition:
SELECT cust_nbr, name, region_id
FROM customer
WHERE region_id = 8;
CUST_NBR NAME REGION_ID
---------- ------------------------------ ----------
16 Paulson Labs 8
17 Evans Supply Corp. 8
18 Spalding Medical Inc. 8
19 Kendall-Taylor Corp. 8
20 Malden Labs 8
,ch01.8459 Page 6 Wednesday, March 27, 2002 2:18 PM

This is the Title of the Book, eMatter Edition
Copyright © 2002 O’Reilly & Associates, Inc. All rights reserved.DML Statements|
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Our result set now includes only those customers residing in the region with a
region_id of 8.But what if we want to specify a region by name instead of region_id?
We could query the region table for a particular name and then query the customer
table using the retrieved region_id.Instead of issuing two different queries, however,
we could produce the same outcome using a single query by introducing ajoin, as in:
SELECT customer.cust_nbr, customer.name, region.name
FROM customer, region
WHERE region.name = 'New England'
AND region.region_id = customer.region_id;
CUST_NBR NAME