Creating Left Joins : Left Join « Join « SQL / MySQL






  1. SQL / MySQL
  2. Join
  3. Left Join

Creating Left Joins

     
mysql>
mysql> CREATE TABLE Books
    -> (
    ->     BookID SMALLINT NOT NULL PRIMARY KEY,
    ->     BookTitle VARCHAR(60) NOT NULL,
    ->     Copyright YEAR NOT NULL
    -> )
    -> ENGINE=INNODB;
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql> INSERT INTO Books VALUES
    -> (12786, 'Notebook', 1934),
    -> (13331, 'C++', 1919),
    -> (14356, 'Opera', 1966),
    -> (15729, 'Sql Server', 1932),
    -> (16284, 'C', 1996),
    -> (17695, 'Pascal', 1980),
    -> (19264, 'Postcards', 1992),
    -> (19354, 'Oracle', 1993);
Query OK, 8 rows affected (0.00 sec)
Records: 8  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql> CREATE TABLE Authors
    -> (
    ->     AuthID SMALLINT NOT NULL PRIMARY KEY,
    ->     AuthFN VARCHAR(20),
    ->     AuthMN VARCHAR(20),
    ->     AuthLN VARCHAR(20)
    -> )
    -> ENGINE=INNODB;
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql> INSERT INTO Authors VALUES
    -> (1006, 'Hunter', 'S.', 'Thompson'),
    -> (1007, 'Joyce', 'Carol', 'Oates'),
    -> (1008, 'Black', NULL, 'Elk'),
    -> (1009, 'Rainer', 'Maria', 'Rilke'),
    -> (1010, 'John', 'Kennedy', 'Toole'),
    -> (1011, 'John', 'G.', 'Neihardt'),
    -> (1012, 'Annie', NULL, 'Proulx'),
    -> (1013, 'Alan', NULL, 'Watts'),
    -> (1014, 'Nelson', NULL, 'Algren');
Query OK, 9 rows affected (0.00 sec)
Records: 9  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql> CREATE TABLE AuthorBook
    -> (
    ->     BookID SMALLINT NOT NULL,
    ->     AuthID SMALLINT NOT NULL,
    ->     PRIMARY KEY (AuthID, BookID)
    -> )
    -> ENGINE=INNODB;
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql> INSERT INTO AuthorBook VALUES
    -> (1006, 14356),
    -> (1008, 15729),
    -> (1009, 12786),
    -> (1010, 17695),
    -> (1011, 15729),
    -> (1012, 19264),
    -> (1012, 19354),
    -> (1014, 16284);
Query OK, 8 rows affected (0.00 sec)
Records: 8  Duplicates: 0  Warnings: 0

mysql>
mysql> SELECT BookTitle, Copyright, AuthID
    -> FROM Books AS b LEFT JOIN AuthorBook AS ab
    -> ON b.BookID=ab.BookID
    -> ORDER BY BookTitle;
+------------+-----------+--------+
| BookTitle  | Copyright | AuthID |
+------------+-----------+--------+
| C          |      1996 |   NULL |
| C++        |      1919 |   NULL |
| Notebook   |      1934 |   NULL |
| Opera      |      1966 |   NULL |
| Oracle     |      1993 |   NULL |
| Pascal     |      1980 |   NULL |
| Postcards  |      1992 |   NULL |
| Sql Server |      1932 |   NULL |
+------------+-----------+--------+
8 rows in set (0.00 sec)

mysql>
mysql> drop table AuthorBook;
Query OK, 0 rows affected (0.00 sec)

mysql> drop table Authors;
Query OK, 0 rows affected (0.00 sec)

mysql> drop table Books;
Query OK, 0 rows affected (0.00 sec)








Related examples in the same category

1.LEFT JOIN tables
2.'USING' command in LEFT JOIN
3.Two LEFT JOIN in select command
4.Two LEFT JOIN
5.Creating the table list with LEFT JOIN and then forming the linking connection with ON
6.A LEFT JOIN and a regular join
7.To list each author record, whether or not there are any book records for it, use a LEFT JOIN
8.To force each category to be displayed, use a reference table and a LEFT JOIN.
9.Replacing the ON clause with the USING clause for Left Join
10.Use a left join to link more than two tables.
11.Addition of the LEFT keyword to each join definition
12.Left Joins (Left Outer Joins)
13.Performing a LEFT JOIN on just the customer and sales tables.
14.Table order in a LEFT JOIN is important.
15.Left outer join syntax
16.Left outer join then order
17.Left outer join
18.Left outer join with using clause
19.Left outer join with subquery
20.Query from left outer join
21.To return all the sales reps who have not yet made a sale