Deleting Data in MySQL
By: Sathya Narayana Printer Friendly Format
To delete a given row or set of rows, you use the DELETE FROM...WHERE command. For instance, you can delete the book called Mr Bunny's Guide to JDO with this command:
mysql> DELETE FROM book -> WHERE title = "Mr Bunny's Guide to JDO";
Now execute a SELECT command to retrieve all books from the table, and you'll see that the record for that book no longer appears:
+----+-------------------------------------------+-------+ | id | title | price | +----+-------------------------------------------+-------+ | 1 | Lord of the Things | 8.99 | | 3 | Parachuting for You and Your Kangaroo | 19.99 | +----+-------------------------------------------+-------+
Note |
Be careful when using DELETE because once a row is removed, it's lost forever. Hence, be particularly wary when specifying a nonunique column in the WHERE clause, such as you have here. In your small database, you know that only a single row will be deleted, but in a real-world database, you can easily end up accidentally deleting a whole bunch of records if you use a badly thought-out WHERE clause. You can reduce the chances of this happening by specifying a WHERE clause on a uniquely valued field (such as a primary key). |
We've now covered enough of the basics of the SQL syntax to move on and show how you can use it to access databases in a JSP page.
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