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Returning results from procedures
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When a SELECT statement is executed, the server retrieves the results of the
SELECT statement and places the results in the variables. If the query results
contain more than one row, the server returns an error. For queries returning
more than one row, cursors must be used. For information about returning
more than one row from a procedure, see “Returning result sets from
procedures”.
If the query results in no rows being selected, a
row not found
warning is returned.
The following procedure returns the results of a single-row SELECT statement
in the procedure parameters.
To return the number of orders placed by a given customer, type the following:
CREATE PROCEDURE OrderCount (IN customer_ID INT,
OUT Orders INT)
BEGIN
SELECT COUNT(DBA.sales_order.id)
INTO Orders
FROM DBA.customer
KEY LEFT OUTER JOIN DBA.sales_order
WHERE DBA.customer.id = customer_ID;
END
You can test this procedure in DBISQL using the following statements, which
show the number of orders placed by the customer with ID 102:
CREATE VARIABLE orders INT;
CALL OrderCount ( 102, orders );
SELECT orders;
Notes
•The customer_ID parameter is declared as an IN parameter. This
parameter holds the customer ID that is passed in to the procedure.
•The Orders parameter is declared as an OUT parameter. It holds the value
of the orders variable that is returned to the calling environment.
• No DECLARE statement is required for the Orders variable, as it is
declared in the procedure argument list.
• The SELECT statement returns a single row and places it into the variable
Orders.