数据库系统基础教程第九章答案.docVIP

数据库系统基础教程第九章答案 9.3.1 a) In the following, we use macro NOT_FOUND as defined in the section. void closestMatchPC() { EXEC SQL BEGIN DECLARE SECTION; char manf, SQLSTATE[6]; int targetPrice, /* holds price given by user */ float tempSpeed, speedOfClosest; char tempModel[4], modelOfClosest[4]; int tempPrice, priceOfClosest; /* for tuple just read from PC amp; closest price found so far */ EXEC SQL END DECLARE SECTION; EXEC SQL DECLARE pcCursor CURSOR FOR SELECT model, price, speed FROM PC; EXEC SQL OPEN pcCursor; /* ask user for target price and read the answer into variable targetPrice */ /* Initially, the first PC is the closest to the target price. If PC is empty, we cannot answer the question, and so abort. */ EXEC SQL FETCH FROM pcCursor INTO :modelOfClosest, :priceOfClosest, :speedOfClosest; if(NOT_FOUND) /* print message and exit */ ; while(1) { EXEC SQL FETCH pcCursor INTO :tempModel, :tempPrice, :tempSpeed; if(NOT_FOUND) break; if(/*tempPrice closer to targetPrice than is priceOfClosest */) { modelOfClosest = tempModel; priceOfClosest = tempPrice; speedOfClosest = tempSpeed; } } /* Now, modelOfClosest is the model whose price is closest to target. We must get its manufacturer with a single-row select */ EXEC SQL SELECT maker INTO :manf FROM Product WHERE model = :modelOfClosest; printf(quot;manf=%s, model=%d, speed=%d\nquot;, manf, modelOfClosest, speedOfClosest); EXEC SQL CLOSE CURSOR pcCursor; } b) void acceptableLaptop() { EXEC SQL BEGIN DECLARE SECTION; int minRam, minHd, minScreen; /* given by user */ float minSpeed; char model[4], maker, float speed; int ram, hd, screen, price; EXEC SQL END DECLARE SECTION; EXEC SQL PREPARE query1 FROM ?SELECT model, speed, ram, hd, screen, price, maker FROM Laptop l, Product p WHERE speed gt;= ? AND ram gt;= ? AND hd gt;= ? AND screen gt;= ? AND l.model = p.model? EXEC SQL DECLARE cursor1 CURSOR FOR query1; /* ask user for minimum sp