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AUTO_INCREMENT
Here are examples of how to solve some common problems with MySQL.
Some of the examples use the table shop
to hold
the price of each article (item number) for certain traders
(dealers). Supposing that each trader has a single fixed price per
article, then (article
,
dealer
) is a primary key for the records.
Start the command-line tool mysql and select a database:
shell> mysql your-database-name
(In most MySQL installations, you can use the database named
test
).
You can create and populate the example table with these statements:
CREATE TABLE shop ( article INT(4) UNSIGNED ZEROFILL DEFAULT '0000' NOT NULL, dealer CHAR(20) DEFAULT '' NOT NULL, price DOUBLE(16,2) DEFAULT '0.00' NOT NULL, PRIMARY KEY(article, dealer)); INSERT INTO shop VALUES (1,'A',3.45),(1,'B',3.99),(2,'A',10.99),(3,'B',1.45), (3,'C',1.69),(3,'D',1.25),(4,'D',19.95);
After issuing the statements, the table should have the following contents:
SELECT * FROM shop; +---------+--------+-------+ | article | dealer | price | +---------+--------+-------+ | 0001 | A | 3.45 | | 0001 | B | 3.99 | | 0002 | A | 10.99 | | 0003 | B | 1.45 | | 0003 | C | 1.69 | | 0003 | D | 1.25 | | 0004 | D | 19.95 | +---------+--------+-------+
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