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CHAPTER 6 Using Procedures and Batches
241
A command delimiter is required after every statement in a statement list
except for the last, where it is optional.
Declarations in compound statements
Local declarations in a compound statement immediately follow the BEGIN
keyword. These local declarations exist only within the compound statement.
The following may be declared within a compound statement:
• Variables
•Cursors
• Temporary tables
• Exceptions (error identifiers)
Local declarations can be referenced by any statement in that compound
statement, or in any compound statement nested within it. Local declarations
are not visible to other procedures called from the compound statement.
The following user-defined function illustrates local declarations of variables.
The
customer table includes some Canadian customers sprinkled among those
from the USA, but there is no
country column. The user-defined function
nationality uses the fact that the US zip code is numeric while the Canadian
postal code begins with a letter to distinguish Canadian and US customers.
CREATE FUNCTION nationality( cust_id INT )
RETURNS CHAR( 20 )
BEGIN
DECLARE natl CHAR(20);
IF cust_id IN ( SELECT id FROM customer
WHERE LEFT(zip,1) > ’9’) THEN
SET natl = ’CDN’;
ELSE
SET natl = ’USA’;
END IF;
RETURN ( natl );
END
This example declares a variable natl to hold the nationality string, uses a SET
statement to set a value for the variable, and returns the value of the natl string
to the calling environment.
The following query lists all Canadian customers in the
customer table:
SELECT *