Join three tables : Simple JOIN « Join « SQL / MySQL

1. SQL / MySQL
2. Join
3. Simple JOIN

Join three tables

  
/*
mysql> SELECT ArticleTitle, Copyright, CONCAT_WS(' ', AuthorFirstName, AuthorMid
dleName, AuthorLastName) AS Author
    -> FROM Articles AS b, AuthorArticle AS ab, Authors AS a
    -> WHERE b.ArticleID=ab.ArticleID AND ab.AuthID=a.AuthID AND Copyright<1980
    -> ORDER BY ArticleTitle;
+-------------------+-----------+-------------------+
| ArticleTitle      | Copyright | Author            |
+-------------------+-----------+-------------------+
| Buy a paper       |      1932 | James Elk         |
| Buy a paper       |      1932 | Mary G. Lee       |
| How write a paper |      1934 | Tom M Ride        |
| Sell a paper      |      1966 | Henry S. Thompson |
+-------------------+-----------+-------------------+
4 rows in set (0.00 sec)

mysql>
*/

Drop table Articles;
Drop table Authors;
Drop table AuthorArticle;



CREATE TABLE Articles (
   ArticleID SMALLINT NOT NULL PRIMARY KEY,
   ArticleTitle VARCHAR(60) NOT NULL,
   Copyright YEAR NOT NULL
)
ENGINE=INNODB;


INSERT INTO Articles VALUES (12786, 'How write a paper', 1934),
                            (13331, 'Publish a paper', 1919),
                            (14356, 'Sell a paper', 1966),
                            (15729, 'Buy a paper', 1932),
                            (16284, 'Conferences', 1996),
                            (17695, 'Journal', 1980),
                            (19264, 'Information', 1992),
                            (19354, 'AI', 1993);


CREATE TABLE Authors (
   AuthID SMALLINT NOT NULL PRIMARY KEY,
   AuthorFirstName VARCHAR(20),
   AuthorMiddleName VARCHAR(20),
   AuthorLastName VARCHAR(20)
)
ENGINE=INNODB;


INSERT INTO Authors VALUES (1006, 'Henry', 'S.', 'Thompson'),
                           (1007, 'Jason', 'Carol', 'Oak'),
                           (1008, 'James', NULL, 'Elk'),
                           (1009, 'Tom', 'M', 'Ride'),
                           (1010, 'Jack', 'K', 'Ken'),
                           (1011, 'Mary', 'G.', 'Lee'),
                           (1012, 'Annie', NULL, 'Peng'),
                           (1013, 'Alan', NULL, 'Wang'),
                           (1014, 'Nelson', NULL, 'Yin');


CREATE TABLE AuthorArticle (
   AuthID SMALLINT NOT NULL,
   ArticleID SMALLINT NOT NULL,
   PRIMARY KEY (AuthID, ArticleID),
   FOREIGN KEY (AuthID) REFERENCES Authors (AuthID),
   FOREIGN KEY (ArticleID) REFERENCES Articles (ArticleID)
)
ENGINE=INNODB;


INSERT INTO AuthorArticle VALUES (1006, 14356), 
                              (1008, 15729), 
                              (1009, 12786), 
                              (1010, 17695),
                              (1011, 15729), 
                              (1012, 19264), 
                              (1012, 19354), 
                              (1014, 16284);
  
SELECT ArticleTitle, Copyright, CONCAT_WS(' ', AuthorFirstName, AuthorMiddleName, AuthorLastName) AS Author
FROM Articles AS b, AuthorArticle AS ab, Authors AS a
WHERE b.ArticleID=ab.ArticleID AND ab.AuthID=a.AuthID AND Copyright<1980
ORDER BY ArticleTitle;

           
         
    
  

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