Using DELETE LOW_PRIORITY command : Delete « Insert Delete Update « SQL / MySQL






Using DELETE LOW_PRIORITY command

    
/*

mysql> select * from Orders;
+---------+--------+----------+---------------------+
| OrderID | BookID | Quantity | DateOrdered         |
+---------+--------+----------+---------------------+
|    1001 |    103 |        1 | 2004-01-12 12:30:00 |
|    1002 |    101 |        1 | 2001-02-12 12:31:00 |
|    1003 |    103 |        2 | 2002-03-12 12:34:00 |
|    1004 |    104 |        3 | 2003-04-12 12:36:00 |
|    1005 |    102 |        1 | 2004-05-12 12:41:00 |
|    1006 |    103 |        2 | 2001-06-12 12:59:00 |
|    1007 |    101 |        1 | 2002-07-12 13:01:00 |
|    1008 |    103 |        1 | 2003-08-12 13:02:00 |
|    1009 |    102 |        4 | 2004-09-12 13:22:00 |
|    1010 |    101 |        2 | 2005-11-12 13:30:00 |
|    1011 |    103 |        1 | 2006-12-12 13:32:00 |
|    1012 |    105 |        1 | 2001-02-12 13:40:00 |
|    1013 |    106 |        2 | 2002-04-12 13:44:00 |
|    1014 |    103 |        1 | 2003-06-12 14:01:00 |
|    1015 |    106 |        1 | 2005-01-12 14:05:00 |
|    1016 |    104 |        2 | 2003-11-12 14:28:00 |
|    1017 |    105 |        1 | 2002-03-12 14:31:00 |
|    1018 |    102 |        1 | 2001-05-12 14:32:00 |
|    1019 |    106 |        3 | 2003-07-12 14:49:00 |
|    1020 |    103 |        1 | 2004-01-12 14:51:00 |
+---------+--------+----------+---------------------+
20 rows in set (0.01 sec)

mysql> DELETE LOW_PRIORITY FROM Orders
    -> WHERE BookID=103
    -> ORDER BY DateOrdered DESC
    -> LIMIT 1;
Query OK, 1 row affected (0.03 sec)

mysql> select * from Orders;
+---------+--------+----------+---------------------+
| OrderID | BookID | Quantity | DateOrdered         |
+---------+--------+----------+---------------------+
|    1001 |    103 |        1 | 2004-01-12 12:30:00 |
|    1002 |    101 |        1 | 2001-02-12 12:31:00 |
|    1003 |    103 |        2 | 2002-03-12 12:34:00 |
|    1004 |    104 |        3 | 2003-04-12 12:36:00 |
|    1005 |    102 |        1 | 2004-05-12 12:41:00 |
|    1006 |    103 |        2 | 2001-06-12 12:59:00 |
|    1007 |    101 |        1 | 2002-07-12 13:01:00 |
|    1008 |    103 |        1 | 2003-08-12 13:02:00 |
|    1009 |    102 |        4 | 2004-09-12 13:22:00 |
|    1010 |    101 |        2 | 2005-11-12 13:30:00 |
|    1012 |    105 |        1 | 2001-02-12 13:40:00 |
|    1013 |    106 |        2 | 2002-04-12 13:44:00 |
|    1014 |    103 |        1 | 2003-06-12 14:01:00 |
|    1015 |    106 |        1 | 2005-01-12 14:05:00 |
|    1016 |    104 |        2 | 2003-11-12 14:28:00 |
|    1017 |    105 |        1 | 2002-03-12 14:31:00 |
|    1018 |    102 |        1 | 2001-05-12 14:32:00 |
|    1019 |    106 |        3 | 2003-07-12 14:49:00 |
|    1020 |    103 |        1 | 2004-01-12 14:51:00 |
+---------+--------+----------+---------------------+
19 rows in set (0.00 sec)


*/

Drop table Orders;


CREATE TABLE Orders
(
   OrderID SMALLINT NOT NULL PRIMARY KEY,
   BookID SMALLINT NOT NULL,
   Quantity TINYINT (40) NOT NULL DEFAULT 1,
   DateOrdered TIMESTAMP,
   FOREIGN KEY (BookID) REFERENCES Books (BookID)
)
ENGINE=INNODB;


INSERT INTO Orders VALUES (1001, 103, 1, '2004-01-12 12:30:00'),
                          (1002, 101, 1, '2001-02-12 12:31:00'),
                          (1003, 103, 2, '2002-03-12 12:34:00'),
                          (1004, 104, 3, '2003-04-12 12:36:00'),
                          (1005, 102, 1, '2004-05-12 12:41:00'),
                          (1006, 103, 2, '2001-06-12 12:59:00'),
                          (1007, 101, 1, '2002-07-12 13:01:00'),
                          (1008, 103, 1, '2003-08-12 13:02:00'),
                          (1009, 102, 4, '2004-09-12 13:22:00'),
                          (1010, 101, 2, '2005-11-12 13:30:00'),
                          (1011, 103, 1, '2006-12-12 13:32:00'),
                          (1012, 105, 1, '2001-02-12 13:40:00'),
                          (1013, 106, 2, '2002-04-12 13:44:00'),
                          (1014, 103, 1, '2003-06-12 14:01:00'),
                          (1015, 106, 1, '2005-01-12 14:05:00'),
                          (1016, 104, 2, '2003-11-12 14:28:00'),
                          (1017, 105, 1, '2002-03-12 14:31:00'),
                          (1018, 102, 1, '2001-05-12 14:32:00'),
                          (1019, 106, 3, '2003-07-12 14:49:00'),
                          (1020, 103, 1, '2004-01-12 14:51:00');

select * from Orders;

DELETE LOW_PRIORITY FROM Orders
WHERE BookID=103
ORDER BY DateOrdered DESC
LIMIT 1;

select * from Orders;

           
         
    
    
    
  








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