Update records with calculation based on two tables : Update « Insert Delete Update « SQL / MySQL

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SQL / MySQL » Insert Delete Update » Update 
Update records with calculation based on two tables

/*
mysql> select * from Books;
+--------+-----------+---------+
| BookID | BookName  | InStock |
+--------+-----------+---------+
|      1 | Poet      |    1934 |
|      2 | Ohio      |    1919 |
|      3 | Angels    |    1966 |
|      4 | Black     |    1932 |
|    101 | Writing   |      10 |
|    102 | News      |      17 |
|    103 | Angels    |      23 |
|    104 | Poet      |      32 |
|    105 | Dunces    |       6 |
|    106 | Solitude  |      28 |
|    107 | Postcards |    1992 |
|    108 | The       |    1993 |
+--------+-----------+---------+
12 rows in set (0.00 sec)

mysql> UPDATE Books, Orders
    -> SET Books.InStock=Books.InStock-Orders.Quantity
    -> WHERE Books.BookID=Orders.BookID
    ->    AND Orders.OrderID=1002;
Query OK, 1 row affected (0.08 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from Books;
+--------+-----------+---------+
| BookID | BookName  | InStock |
+--------+-----------+---------+
|      1 | Poet      |    1934 |
|      2 | Ohio      |    1919 |
|      3 | Angels    |    1966 |
|      4 | Black     |    1932 |
|    101 | Writing   |       9 |
|    102 | News      |      17 |
|    103 | Angels    |      23 |
|    104 | Poet      |      32 |
|    105 | Dunces    |       6 |
|    106 | Solitude  |      28 |
|    107 | Postcards |    1992 |
|    108 | The       |    1993 |
+--------+-----------+---------+
12 rows in set (0.01 sec)


*/

Drop table Books;
Drop table Orders;
       
CREATE TABLE Books
(
   BookID SMALLINT NOT NULL PRIMARY KEY,
   BookName VARCHAR(40NOT NULL,
   InStock SMALLINT NOT NULL
)
ENGINE=INNODB;


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


INSERT INTO Orders VALUES (10011031'2004-01-12 12:30:00'),
                          (10021011'2001-02-12 12:31:00'),
                          (10031032'2002-03-12 12:34:00'),
                          (10041043'2003-04-12 12:36:00'),
                          (10051021'2004-05-12 12:41:00'),
                          (10061032'2001-06-12 12:59:00'),
                          (10071011'2002-07-12 13:01:00'),
                          (10081031'2003-08-12 13:02:00'),
                          (10091024'2004-09-12 13:22:00'),
                          (10101012'2005-11-12 13:30:00'),
                          (10111031'2006-12-12 13:32:00'),
                          (10121051'2001-02-12 13:40:00'),
                          (10131062'2002-04-12 13:44:00'),
                          (10141031'2003-06-12 14:01:00'),
                          (10151061'2005-01-12 14:05:00'),
                          (10161042'2003-11-12 14:28:00'),
                          (10171051'2002-03-12 14:31:00'),
                          (10181021'2001-05-12 14:32:00'),
                          (10191063'2003-07-12 14:49:00'),
                          (10201031'2004-01-12 14:51:00');


INSERT INTO Books VALUES (101'Writing', 12),
                         (102'News', 17),
                         (103'Angels', 23),
                         (104'Poet', 32),
                         (105'Dunces', 6),
                         (106'Solitude', 28);


select from Books;

UPDATE Books, Orders
SET Books.InStock=Books.InStock-Orders.Quantity
WHERE Books.BookID=Orders.BookID
   AND Orders.OrderID=1002;


select from Books;

           
       
Related examples in the same category
1. Do PLUS calculation in where clause
2. Assign value in select clause
3. Modifying Row Data
4. Update with limitation and calculation
5. Update two tables with calculation
6. Using UPDATE Statements to Modify Data in Joined Tables
7. Update with condition
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