Sub query with EXISTS command : Exists « Select Clause « SQL / MySQL

1. SQL / MySQL
2. Select Clause
3. Exists

Sub query with EXISTS command

   
/*

mysql> SELECT ArticleID, ArticleTitle
    -> FROM Articles AS b
    -> WHERE EXISTS
    ->    (
    ->       SELECT ArticleID
    ->       FROM AuthorArticle AS ab
    ->       WHERE b.ArticleID=ab.ArticleID
    ->    )
    -> ORDER BY ArticleTitle;
+-----------+-------------------+
| ArticleID | ArticleTitle      |
+-----------+-------------------+
|     19354 | AI                |
|     15729 | Buy a paper       |
|     16284 | Conferences       |
|     12786 | How write a paper |
|     19264 | Information       |
|     17695 | Journal           |
|     14356 | Sell a paper      |
+-----------+-------------------+
7 rows in set (0.01 sec)


*/       
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 ArticleID, ArticleTitle
FROM Articles AS b
WHERE EXISTS
   (
      SELECT ArticleID
      FROM AuthorArticle AS ab
      WHERE b.ArticleID=ab.ArticleID
   )
ORDER BY ArticleTitle;



           
         
    
    
  

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