Windows 2003 server web - LISTING_NUMBER_OF_BIDS INTEGER FORMAT 999 NULL, LISTING_WINNING_PRICE MONEY NULL,
LISTING_NUMBER_OF_BIDS INTEGER FORMAT 999 NULL, LISTING_WINNING_PRICE MONEY NULL, LISTING_BID_INCREMENT MONEY NULL, BID_PRICE MONEY NULL ); The LISTING_NUMBER_OF_BIDS is output formatted as for number of bids in the OLTP database model LISTING table. Encoding Business Rules As with the previous section covering individual field business rules, this section covers the case study online auction house database models, but this time attempting to encode a few things into a pseudo database programming language. The intention here is to demonstrate what can be done. It is a matter for some debate among computer professionals as to whether business rules should be written into stored procedures. Some think implementing business rules in stored procedures is good for some reasons. Others consider that applications handle this type of complexity more effectively and efficiently. Encoding Business Rules for the OLTP Database Model You already know the difference between a stored procedure, a stored function, and an event-based trigger. What can be done to the OLTP database model for this case study, to utilize some type of database stored coding? The BID table is a good candidate for some basic stored functions: CREATE TABLE BID ( LISTING# CHAR(10) NOT NULL, BUYER_ID INTEGER FOREIGN KEY REFERENCES BUYER NOT NULL, BID_PRICE MONEY CHECK(VERIFY_BID(LISTING#, BID_PRICE)) NOT NULL, PROXY_BID MONEY CHECK(PROXY_BID > BID_PRICE AND VERIFY_BID(LISTING#, PROXY_BID)) NULL, BID_DATE DATE FORMAT DD MON, YEAR NOT NULL, CONSTRAINT PRIMARY KEY (LISTING#, BUYER_ID) ); The preceding script has a CHECK constraint on the BID_PRICE and PROXY_BID fields. Both of these CHECK constraints execute a function. A bid price is entered by a bidder. That bid price must exceed the starting and current prices, both of which are stored in the listing table. This can be encoded using a stored function as follows: CREATE FUNCTION VERIFY_BID(LISTNUM CHAR(10), BID MONEY DEFAULT NULL) RETURN BOOLEAN DECLARE START_PRICE MONEY; 373 Business Rules and Field Settings
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