SQL评估查询

时间：2018-09-28 13:31:46

标签： sql oracle

我对以下查询感到困惑。

  1. 显示订购最多的客户的全名和电话号码。

  2. 哪个项目最畅销？显示说明和价格。

附有我的ERD。

create table statements are as follows:
CREATE TABLE ITEMS (
itemID number(5),
itemDescription varchar2(60),
itemSize varchar2(22),       
itemColour varchar2(10),
itemPrice number (5,2),
itemQuantityAvailable number(3),
CONSTRAINT pk_items PRIMARY KEY (itemID));

CREATE TABLE CUSTOMERS (
custID number(5),
custLName varchar2(10),
custFName varchar2(20),
custAddress varchar2(30),
custTown varchar2(20),
custPostcode number(4),
custPhone number(10),
custEmail varchar2(30),
shopID number(5),
CONSTRAINT pk_customers PRIMARY KEY (custID),
CONSTRAINT fk_customers_shopID FOREIGN KEY (shopID)
REFERENCES SHOPS (shopID));

CREATE TABLE ORDERS (
orderNo number(5),
orderDate Date,
dispatchDate date,
custID number(5),
CONSTRAINT pk_orders PRIMARY KEY (orderNo),
CONSTRAINT fk_orders_custID FOREIGN KEY (custID)
REFERENCES CUSTOMERS (custID));

CREATE TABLE OrderQuantity (
orderNo number(5),
itemID number(5),
orderQuantity number(3),
CONSTRAINT pk_orderQty PRIMARY KEY (itemID, orderNo),
CONSTRAINT fk_orderQty_itemID FOREIGN KEY (itemID)
REFERENCES ITEMS (itemID),
CONSTRAINT fk_orderQty_orderNo FOREIGN KEY (orderNO)
REFERENCES ORDERS (orderNo));

插入语句如下：

INSERT INTO ITEMS VALUES (1,'ADIDAS MEN''S ID STADIUM FULL-ZIP JACKET','S/M/L/XL','Silver',89.99,100);
INSERT INTO ITEMS VALUES (2,'ADIDAS MEN''S ESSENTIALS 3 STRIPES CREW FRENCH TERRY','S/L/XL','Black',71.99,90);
INSERT INTO ITEMS VALUES (3,'ADIDAS MEN''s ESSENTIALS 3-STRIPES FLEECE PANT','M/L/XL/XXL','White',62.99,80);
INSERT INTO ITEMS VALUES (4,'NIKE MEN''S FULL-ZIP SPORTSWEAR HOODIE','M/L/XL','DarkGrey',67.49,70);
INSERT INTO ITEMS VALUES (5,'NIKE MEN''S HBR FLEECE CREW','S/L/XL','DarkGrey',58.49,60);
INSERT INTO ITEMS VALUES (6,'PUMA MEN''S ESSENTIAL SWEAT PANTS','XS/S/M/L/XL','Navy',45.00,50);
INSERT INTO ITEMS VALUES (7,'ADIDAS MEN''S ESSENTIALS CHELSEA SHORTS','M/L/XL','Green',35.99,40);
INSERT INTO ITEMS VALUES (8,'PUMA MEN''S CORE 7IN RUNNING SHORTS','S/L/XL','Black',26.99,20);
INSERT INTO ITEMS VALUES (9,'ASICS GT 2000 6 MEN''S RUNNING SHOES','8/8.5/9/9.5/10','Silver',239.00,90);
INSERT INTO ITEMS VALUES (10,'ASICS GEL-KAYANO 25 2E WIDE MEN''S RUNNING SHOE','9/9.5/10/10.5/11','Black',219.00,60);
INSERT INTO ITEMS VALUES (11,'REEBOK RUNNER 3.0 MEN''S RUNNING SHOES','8/8.5/10/10.5','Orange',209.00,10);
INSERT INTO ITEMS VALUES (12,'REEBOK MEN''S WORKOUT READY 2.0 TEE','XS/S/M','White',199.00,50);
INSERT INTO ITEMS VALUES (13,'UNDER ARMOUR RAPID MEN''S RUNNING SHOES','8.5/10/11','Black',199.00,20);
INSERT INTO ITEMS VALUES (14,'UNDER ARMOUR CHARGED MEN''S RUNNING SHOES','8/8.5/9/9.5/10','Silver',159.00,80);
INSERT INTO ITEMS VALUES (15,'ADIDAS SOLAR DRIVE MEN''S RUNNING SHOE','8/8.5/10/10.5','Black',139.00,30);


INSERT INTO CUSTOMERS VALUES (1,'Widimer','Cindy','121 King St','Box Hill',3195,0470121566,'cindy_widimer@gmail.com',1);
INSERT INTO CUSTOMERS VALUES (2,'Bohrman','Robert','54 Queens St','Murrumbeena',3195,0455131565,'robert_bohram@gmail.com',3);
INSERT INTO CUSTOMERS VALUES (3,'Clarke','Brenda','89 Pecket St','Oakleigh',3195,0424456123,'brenda.clarke@gmail.com',2);
INSERT INTO CUSTOMERS VALUES (4,'Cartier','Bruce','12 Parkore St','Mulgrave',3195,0425654123,'bruce.cartier@gmail.com',3);
INSERT INTO CUSTOMERS VALUES (5,'Heart','Lucy','45 Rose St','Hampton Park',3178,0470456321,'lucy.heart@gmail.com',1);
INSERT INTO CUSTOMERS VALUES (6,'Carter','Joan','123 Davdison St','Hampton Park',3178,0452123789,'carter_joangmail.com',3);
INSERT INTO CUSTOMERS VALUES (7,'John','Ailene','56 Spring St','Yaraman',3178,0475123159,'john.ailene@gmail.com',1);
INSERT INTO CUSTOMERS VALUES (8,'Lewis','Carl','45 Brendon Ct','Noble Park',3178,0454789456,'carl_lewis@gmail.com',3);
INSERT INTO CUSTOMERS VALUES (9,'Holden','Hilary','56 Swanston St','Sunshine',3020,0421456123,'hilar_holdengmail.com',1);
INSERT INTO CUSTOMERS VALUES (10,'Powell','Venus','124 Russel St','Richmond',3112,0431456753,'venus_powellgmail.com',2);
INSERT INTO CUSTOMERS VALUES (11,'Juliet','Susan','87 Fawkner Ct','South Yara',3141,0424687423,'susan_juliet@gmail.com',2);
INSERT INTO CUSTOMERS VALUES (12,'Price','Victor','125 William St','Flagstaff',3003,0465789123,'victor_price@gmail.com',2);


INSERT INTO ORDERS VALUES (1,'01/Jan/18','03/Feb/18',1);
INSERT INTO ORDERS VALUES (2,'20/Jan/18','05/Feb/18',3);
INSERT INTO ORDERS VALUES (3,'05/Feb/18','10/Feb/18',4);
INSERT INTO ORDERS VALUES (4,'18/Feb/18','22/Feb/18',5);
INSERT INTO ORDERS VALUES (5,'01/Mar/18','10/Mar/18',10);
INSERT INTO ORDERS VALUES (6,'12/Mar/18','15/Mar/18',12);
INSERT INTO ORDERS VALUES (7,'07/Apr/18','14/Apr/18',11);
INSERT INTO ORDERS VALUES (8,'25/Apr/18','27/Apr/18',3);
INSERT INTO ORDERS VALUES (9,'06/May/18','10/May/18',2);
INSERT INTO ORDERS VALUES (10,'17/Jun/18','20/Jun/18',5);
INSERT INTO ORDERS VALUES (11,'29/Jun/18','07/Jul/18',4);
INSERT INTO ORDERS VALUES (12,'08/Jul/18','14/Jul/18',11);
INSERT INTO ORDERS VALUES (13,'25/Jul/18','29/Jul/18',12);
INSERT INTO ORDERS VALUES (14,'01/Aug/18','18/Aug/18',5);
INSERT INTO ORDERS VALUES (15,'19/Aug/18','10/Sep/18',1);
INSERT INTO ORDERS VALUES (16,'11/Sep/18','15/Sep/18',4);
INSERT INTO ORDERS VALUES (17,'21/Sep/18','29/Sep/18',5);
INSERT INTO ORDERS VALUES (18,'01/Oct/18',null,10);
INSERT INTO ORDERS VALUES (19,'20/Oct/18',null,3);
INSERT INTO ORDERS VALUES (20,'23/Oct/18',null,1);

INSERT INTO OrderQuantity VALUES (1,1,20);
INSERT INTO OrderQuantity VALUES (2,3,10);
INSERT INTO OrderQuantity VALUES (3,4,20);
INSERT INTO OrderQuantity VALUES (4,5,14);
INSERT INTO OrderQuantity VALUES (5,10,10);
INSERT INTO OrderQuantity VALUES (6,11,15);
INSERT INTO OrderQuantity VALUES (7,12,10);
INSERT INTO OrderQuantity VALUES (8,3,25);
INSERT INTO OrderQuantity VALUES (9,2,50);
INSERT INTO OrderQuantity VALUES (10,5,20);
INSERT INTO OrderQuantity VALUES (11,4,10);
INSERT INTO OrderQuantity VALUES (12,11,20);
INSERT INTO OrderQuantity VALUES (13,12,10);
INSERT INTO OrderQuantity VALUES (14,5,10);
INSERT INTO OrderQuantity VALUES (15,1,10);
INSERT INTO OrderQuantity VALUES (16,4,30);
INSERT INTO OrderQuantity VALUES (17,5,9);
INSERT INTO OrderQuantity VALUES (18,10,30);
INSERT INTO OrderQuantity VALUES (19,3,20);
INSERT INTO OrderQuantity VALUES (20,1,15);

1 个答案:

答案 0 :(得分：0)

您的查询存在几个问题。

您不能在SQL语句的GROUP BY部分中使用聚合函数。 另外，MAX（COUNT（.....显然是错误的。

当您需要提取“聚合的聚合”时，最好的方法是使用“内联视图”（在Oracle术语中）。

例如像这样的东西：

 SELECT c.custid AS custid
      ,custfname||' '||custlname AS cust_fullname
      ,custPhone
      ,num_orders
  FROM customers c
      ,(SELECT custid, num_orders
          FROM (
                SELECT custid,count(*) as num_orders
                  FROM orders
              GROUP BY custid
              ORDER BY 2 desc
          ) all_orders
        WHERE ROWNUM<=1) largest_order
WHERE c.custid=largest_order.custid

从内到外跟踪查询，例如从最内部（或缩进）部​​分开始。 

        SELECT custid,count(*) as num_orders
          FROM orders
        GROUP BY custid
        ORDER BY 2 desc

提取所有监护权的每个监护权的订单数量，并按数量降序对其进行排序。

SELECT custid, num_orders
      FROM (
            SELECT custid,count(*) as num_orders
              FROM orders
          GROUP BY custid
          ORDER BY 2 desc
      ) all_orders
    WHERE ROWNUM<=1

ROWNUM的内容是Oracle选择结果的第一行的方式-“ Oracle的LIMIT子句”。其他一些DB可以更简单些。

然后，最后的查询仅将上述结果与客户表结合在一起以提取全名和电话号码。

还有其他几种方法可以执行此操作-主要涉及子查询等。但是这种方法通常是最快的，而且我认为是最全面的。

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