OCP-1Z0-051-V9.02-137题

137. View the Exhibits and examine PRODUCTS and SALEStables.You issue the following query to display product name andthe number of times the product has beensold: SQL>SELECT p.prod_name,i.item_cnt    FROM (SELECT  prod_id, COUNT(*)item_cnt               FROMsales               GROUP BY prod_id) i RIGHT OUTER JOIN  products p    ON   i.prod_id  = p.prod_id;What happens when the above statement is executed?A. The statement executes successfully and produces therequired output.B. The statement produces an error because ITEM_CNT cannotbe displayed in the outer query.C. The statement produces an error because a subquery in theFROM clause and outer-joins cannot beused together.D. The statement produces an error because the GROUP BYclause cannot be used in a subquery in theFROM clause.Answer: A答案解析：先通过子查询，求出prod_id和销售的次数，然后再和products表右连接，求出产品的名称和销售的次数
实验验证：sh@TEST0924>SELECT p.prod_name, i.item_cnt  2  FROM (SELECT  prod_id, COUNT(*) item_cnt FROM sales GROUP BYprod_id) 3   i RIGHT OUTER JOIN  products p    4  ON   i.prod_id  = p.prod_id;PROD_NAME                                         ITEM_CNT------------------------------------------------------------EnvoyExternal Keyboard                                 3441SIMM-8MB PCMCIAII card                                19557MousePad                                             29282External6X CD-ROM                                     13043...72rows selected.

132. View the Exhibit and examine the structure of theSALES and PRODUCTS tables.In the SALES table, PROD_ID is the foreign keyreferencing PROD_ID in the PRODUCTS table,You want to list each product ID and the number of timesit has been sold.Evaluate the following query:SQL>SELECT p.prod_id, COUNT(s.prod_id)  FROM products p _____________ sales s  ON p.prod_id  = s.prod_id  GROUP BY p.prod_id;Which two JOIN options can be used in the blank in theabove query to get the required output? (Choosetwo.)A. JOIN B. FULL OUTER JOINC. LEFT OUTER JOIND. RIGHT OUTER JOINAnswer: BC答案解析：列出每一个产品ID和产品已销售的次数。列出每一个产品ID，所以C正确，由于s表的prod_id是products表的外键，所以是products的子集，所以B也正确
PS:这两题是相似的，通过不同的方式实现的。