MySQL: Implicit Koşullara katıl: Yinelenen kaldırma için ne tür bir ifade gerekir?

Question

JOIN ifadeleri üzerinde çalışıyorum (örtülü) ve bir çok aksaklık olmadan katılacak kodu kurdum ve kod çalıştığında kişi başına birkaç kopya oluyor. Her bir kişiden sadece birini göstermek için ne tür bir ifade kullanmam gerektiğini merak ediyordum? Eğer kodun diğer kısımlarını gerekiyorsa

Select deyimi

SELECT CONCAT(customers.customer_first_name, ' ', customers.customer_last_name) as 'Customer', 
     orders.order_date as 'Order Date', customers.customer_zip as 'Zipcode' 
FROM customers, orders, order_details 
WHERE order_details.item_id = 10 
ORDER BY CONCAT(customers.customer_first_name, ' ', customers.customer_last_name) ASC; 

, bunlar da hazır.

Tablo/Ekle İfadeler Oluşturma:

/*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); 

Answer 1

Bir Descartes ürününüz var, bir join. distinct anahtar sözcüğünü kullanabilir veya group by yapabilirdiniz, ancak bunun yerine gerçekten bir join'a ihtiyacınız var gibi görünüyor. Senin için böyle bir şey yazıyorum, ama senin table yapısını bilmiyorum çünkü ben sütunları tahmin edilecektir: Doğal

SELECT CONCAT(customers.customer_first_name, ' ', customers.customer_last_name) as 'Customer', 
     orders.order_date as 'Order Date', customers.customer_zip as 'Zipcode' 
FROM order_details 
join orders 
on order_details.order_id = orders.order_id and order_details.item_id = 10 
join customers 
on orders.customer_id = customers.customer_id 
ORDER BY CONCAT(customers.customer_first_name, ' ', customers.customer_last_name) ASC; 

, cunku biz, müşteri başına tek bir kayıt olacak garantisi yoktur , en azından eksik bilgi, birden fazla siparişi olan, her biri sipariş detayına sahip olan hiçbir müşterinin olmadığını varsaymaz. item_id = 10

Answer 2

şu anda büyük olasılıkla Kartezyen ürün alıyorsanız ... Explicit vs implicit SQL joins bakınız. Üzgünüz, bu yorumda değil ... yeni kullanıcı, puan henüz yorum yapmak için yeterince yüksek değil.

Answer 3

JOIN anahtar kelimesini kullanmak istemezseniz, anahtar sütunlarını whick üzerine ekleyebilirsiniz. tabloları aşağıdaki gibi WHERE yan tümce ilgilidir:

SELECT CONCAT(customers.customer_first_name, ' ', customers.customer_last_name) as 'Customer', 
     orders.order_date as 'Order Date', customers.customer_zip as 'Zipcode' 
FROM customers, orders, order_details 
WHERE order_details.item_id = 10 
AND orders.customer_id = customers.customer_id 
AND order_details.order_id = orders.order_id 
ORDER BY CONCAT(customers.customer_first_name, ' ', customers.customer_last_name) ASC;