MySQL：子查询：我怎样才能使它工作？

Question

我有这个任务，我想就说明而言我绝对感到困惑，但我正在构建一个子查询。我确定我做了一些荒谬的事情，但我不知道如何去解决它。有人真正理解这些说明吗？

说明：

8. 使用子查询来确定哪位艺术家在订单中订购的商品数量最多？首先确定上的最高数量 任何订单，然后确定与其关联的商品 ID，然后 展示艺术家。

到目前为止我所拥有的：

SELECT 
       SUM(order_details.order_qty) as 'Order Quantity',
       items.item_ID as 'Item ID',
       artists.artist_name as 'Artist'
FROM orders
JOIN order_details on order_details.order_ID = orders.order_ID
JOIN items on items.item_ID = order_details.item_ID
JOIN artists on items.artist_id = artists.artist_id
WHERE SUM(order_details.order_qty) >
        (SELECT --How can I set this So that the quantity is being compared...this is where I'm stuck.)
GROUP BY items.item_id DESC;

您如何决定使用子查询。它被用在条件子句中……但这是出于比较的原因，是吗？

所有代码：

/*Drop Tables*/
DROP TABLE IF EXISTS customers;
DROP TABLE IF EXISTS orders;
DROP TABLE IF EXISTS order_details;
DROP TABLE IF EXISTS items;
DROP TABLE IF EXISTS artists;
DROP TABLE IF EXISTS employees;

/*Create Tables*/
CREATE TABLE customers
(
 customer_id      INT,
 customer_first_name  VARCHAR(20),
 customer_last_name  VARCHAR(20)   NOT NULL,
 customer_address   VARCHAR(50)  NOT NULL,
 customer_city     VARCHAR(20)   NOT NULL,
 customer_state    CHAR(2)     NOT NULL,
 customer_zip     CHAR(5)   NOT NULL,
 customer_phone    CHAR(10)   NOT NULL,
 customer_fax     CHAR(10),
 CONSTRAINT customers_pk 
 PRIMARY KEY (customer_id)
);

CREATE TABLE artists
(
 artist_id      INT       NOT NULL,
 artist_name  VARCHAR(30),
 CONSTRAINT artist_pk 
 PRIMARY KEY (artist_id)
);

CREATE TABLE items
(
 item_id    INT       NOT NULL,
 title     VARCHAR(50)   NOT NULL,
 artist_id   INT   NOT NULL,
 unit_price  DECIMAL(9,2)  NOT NULL,
 CONSTRAINT items_pk 
  PRIMARY KEY (item_id),
 CONSTRAINT items_fk_artists
  FOREIGN KEY (artist_id) REFERENCES artists (artist_id)
);

CREATE TABLE employees
(
 employee_id     INT        NOT NULL,
 last_name      VARCHAR(20)    NOT NULL,
 first_name     VARCHAR(20)    NOT NULL,
  manager_id     INT,
CONSTRAINT employees_pk 
 PRIMARY KEY (employee_id),
CONSTRAINT emp_fk_mgr FOREIGN KEY (manager_id) REFERENCES employees(employee_id) 
);

CREATE TABLE orders
(
 order_id     INT     NOT NULL,
 customer_id    INT     NOT NULL,
 order_date    DATE    NOT NULL,
 shipped_date   DATE,
 employee_id    INT,
 CONSTRAINT orders_pk
  PRIMARY KEY (order_id),
 CONSTRAINT orders_fk_customers
  FOREIGN KEY (customer_id) REFERENCES customers (customer_id),
CONSTRAINT orders_fk_employees
  FOREIGN KEY (employee_id) REFERENCES employees (employee_id)
);

CREATE TABLE order_details
(
 order_id   INT      NOT NULL,
 item_id    INT      NOT NULL,
 order_qty   INT      NOT NULL,
 CONSTRAINT order_details_pk 
  PRIMARY KEY (order_id, item_id),
 CONSTRAINT order_details_fk_orders
  FOREIGN KEY (order_id)
  REFERENCES orders (order_id),
 CONSTRAINT order_details_fk_items
  FOREIGN KEY (item_id)
  REFERENCES items (item_id)
);

/*Insert Statements*/
INSERT INTO customers VALUES 
(1,'Korah','Blanca','1555 W Lane Ave','Columbus','OH','43221','6145554435','6145553928'),
(2,'Yash','Randall','11 E Rancho Madera Rd','Madison','WI','53707','2095551205','2095552262'),
(3,'Johnathon','Millerton','60 Madison Ave','New York','NY','10010','2125554800',NULL),
(4,'Mikayla','Davis','2021 K Street Nw','Washington','DC','20006','2025555561',NULL),
(5,'Kendall','Mayte','4775 E Miami River Rd','Cleves','OH','45002','5135553043',NULL),
(6,'Kaitlin','Hostlery','3250 Spring Grove Ave','Cincinnati','OH','45225','8005551957','8005552826'),
(7,'Derek','Chaddick','9022 E Merchant Wy','Fairfield','IA','52556','5155556130',NULL),
(8,'Deborah','Davis','415 E Olive Ave','Fresno','CA','93728','5595558060',NULL),
(9,'Karina','Lacy','882 W Easton Wy','Los Angeles','CA','90084','8005557000',NULL),
(10,'Kurt','Nickalus','28210N Avenue Stanford','Valencia','CA','91355','8055550584','055556689'),
(11,'Kelsey','Eulalia','7833 N Ridge Rd','Sacramento','CA','95887','2095557500','2095551302'),
(12,'Anders','Rohansen','12345 E 67th Ave NW','Takoma Park','MD','24512','3385556772',NULL),
(13,'Thalia','Neftaly','2508 W Shaw Ave','Fresno','CA','93711','5595556245',NULL),
(14,'Gonzalo','Keeton','12 Daniel Road','Fairfield','NJ','07004','2015559742',NULL),
(15,'Ania','Irvin','1099 N Farcourt St','Orange','CA','92807','7145559000',NULL),
(16,'Dakota','Baylee','1033 NSycamore Ave.','Los Angeles','CA','90038','2135554322',NULL),
(17,'Samuel','Jacobsen','3433 E Widget Ave','Palo Alto','CA','92711','4155553434',NULL),
(18,'Justin','Javen','828 S Broadway','Tarrytown','NY','10591','8005550037',NULL),
(19,'Kyle','Marissa','789 E Mercy Ave','Phoenix','AZ','85038','9475553900',NULL),
(20,'Erick','Kaleigh','Five Lakepointe Plaza, Ste 500','Charlotte','NC','28217','7045553500',NULL),
(21,'Marvin','Quintin','2677 Industrial Circle Dr','Columbus','OH','43260','6145558600','6145557580'),
(22,'Rashad','Holbrooke','3467 W Shaw Ave #103','Fresno','CA','93711','5595558625','5595558495'),
(23,'Trisha','Anum','627 Aviation Way','Manhatttan Beach','CA','90266','3105552732',NULL),
(24,'Julian','Carson','372 San Quentin','San Francisco','CA','94161','6175550700',NULL),
(25,'Kirsten','Story','2401 Wisconsin Ave NW','Washington','DC','20559','2065559115',NULL);

INSERT INTO artists(artist_id,artist_name) VALUES 
(10,'Umani'),
(11,'The Ubernerds'),
(12,'No Rest For The Weary'),
(13,'Burt Ruggles'),
(14,'Sewed the Vest Pocket'),
(15,'Jess & Odie'),
(16,'Onn & Onn');

INSERT INTO items (item_id,title,artist_id,unit_price) VALUES 
(1,'Umami In Concert',10,17.95),
(2,'Race Car Sounds',11,13),
(3,'No Rest For The Weary',12,16.95),
(4,'More Songs About Structures and Comestibles',12,17.95),
(5,'On The Road With Burt Ruggles',13,17.5),
(6,'No Fixed Address',14,16.95),
(7,'Rude Noises',15,13),
(8,'Burt Ruggles: An Intimate Portrait',13,17.95),
(9,'Zone Out With Umami',10,16.95),
(10,'Etcetera',16,17);

INSERT INTO employees VALUES 
(1,'Smith','Cindy',null),
(2,'Jones','Elmer',1),
(3,'Simonian','Ralph',2),
(9,'Locario','Paulo',1),
(8,'Leary','Rhea',9),
(4,'Hernandez','Olivia',9),
(5,'Aaronsen','Robert',4),
(6,'Watson','Denise',8),
(7,'Hardy','Thomas',2);

INSERT INTO orders VALUES
(19,1,'2012-10-23','2012-10-28',6),
(29,8,'2012-11-05','2012-11-11',6),
(32,11,'2012-11-10','2012-11-13',NULL),
(45,2,'2012-11-25','2012-11-30',NULL),
(70,10,'2012-12-28','2013-01-07',5),
(89,22,'2013-01-20','2013-01-22',7),
(97,20,'2013-01-29','2013-02-02',5),
(118,3,'2013-02-24','2013-02-28',7),
(144,17,'2013-03-21','2013-03-29',NULL),
(158,9,'2013-04-04','2013-04-20',NULL),
(165,14,'2013-04-11','2013-04-13',NULL),
(180,24,'2013-04-25','2013-05-30',NULL),
(231,15,'2013-06-14','2013-06-22',NULL),
(242,23,'2013-06-24','2013-07-06',3),
(264,9,'2013-07-15','2013-07-18',6),
(298,18,'2013-08-18','2013-09-22',3),
(321,2,'2013-09-09','2013-10-05',6),
(381,7,'2013-11-08','2013-11-16',7),
(413,17,'2013-12-05','2014-01-11',7),
(442,5,'2013-12-28','2014-01-03',5),
(479,1,'2014-01-30','2014-03-03',3),
(491,16,'2014-02-08','2014-02-14',5),
(523,3,'2014-03-07','2014-03-15',3),
(548,2,'2014-03-22','2014-04-18',NULL),
(550,17,'2014-03-23','2014-04-03',NULL),
(601,16,'2014-04-21','2014-04-27',NULL),
(607,20,'2014-04-25','2014-05-04',NULL),
(624,2,'2014-05-04','2014-05-09',NULL),
(627,17,'2014-05-05','2014-05-10',NULL),
(630,20,'2014-05-08','2014-05-18',7),
(651,12,'2014-05-19','2014-06-02',7),
(658,12,'2014-05-23','2014-06-02',7),
(687,17,'2014-06-05','2014-06-08',NULL),
(693,9,'2014-06-07','2014-06-19',NULL),
(703,19,'2014-06-12','2014-06-19',7),
(778,13,'2014-07-12','2014-07-21',7),
(796,17,'2014-07-19','2014-07-26',5),
(800,19,'2014-07-21','2014-07-28',NULL),
(802,2,'2014-07-21','2014-07-31',NULL),
(824,1,'2014-08-01',NULL,NULL),
(827,18,'2014-08-02',NULL,NULL),
(829,9,'2014-08-02',NULL,NULL);

INSERT INTO order_details VALUES 
(381,1,1),
(601,9,1),
(442,1,1),
(523,9,1),
(630,5,1),
(778,1,1),
(693,10,1),
(118,1,1),
(264,7,1),
(607,10,1),
(624,7,1),
(658,1,1),
(800,5,1),
(158,3,1),
(321,10,1),
(687,6,1),
(827,6,1),
(144,3,1),
(479,1,2),
(630,6,2),
(796,5,1),
(97,4,1),
(601,5,1),
(800,1,1),
(29,10,1),
(70,1,1),
(165,4,1),
(180,4,1),
(231,10,1),
(413,10,1),
(491,6,1),
(607,3,1),
(651,3,1),
(703,4,1),
(802,3,1),
(824,7,2),
(829,1,1),
(550,4,1),
(796,7,1),
(693,6,1),
(29,3,1),
(32,7,1),
(242,1,1),
(298,1,1),
(479,4,1),
(548,9,1),
(627,9,1),
(778,3,1),
(19,5,1),
(89,4,1),
(242,6,1),
(264,4,1),
(550,1,1),
(693,7,3),
(824,3,1),
(829,5,1),
(829,9,1);

如果您看不懂文字，请告诉我。

Answer 1

好的，让我们重新制作我的答案，首先这是我认为获得请求结果的最简单方法：

SELECT SUM(order_details.order_qty) as 'Order Quantity',
   items.item_ID as 'Item ID',
   artists.artist_name as 'Artist'
FROM order_details
JOIN items on items.item_ID = order_details.item_ID
JOIN artists on items.artist_id = artists.artist_id
GROUP BY order_details.item_ID
ORDER BY SUM(order_details.order_qty) DESC
# LIMIT 1
# You can uncomment the line above if you only want to return the artist with the highest selling item

根据我对说明的最佳解释，使用子查询进行查询：

SELECT artists.artist_name as 'Artist'
FROM artists
JOIN items on items.artist_id = artists.artist_id
WHERE items.item_id =(
    SELECT order_details.item_ID as 'Item ID'
    FROM order_details
    GROUP BY order_details.item_id
    ORDER BY SUM(order_details.order_qty) DESC
    LIMIT 1);

在内部查询中，您从所有商品 ID 中选择销售额最高的商品 ID。然后在外部查询中获取所有艺术家及其项目，并获取拥有等于内部查询结果的 item_id 的艺术家。

（编辑，我在第一次查询中使用了错误的方式注释 MySQL，已修复）