Syntax:
Single-table syntax:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name
    [WHERE where_condition]
    [ORDER BY ...]
    [LIMIT row_count]

Multiple-table syntax:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
    tbl_name[.*] [, tbl_name[.*]] ...
    FROM table_references
    [WHERE where_condition]

Or:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
    FROM tbl_name[.*] [, tbl_name[.*]] ...
    USING table_references
    [WHERE where_condition]

For the single-table syntax, the DELETE statement deletes rows from
tbl_name and returns a count of the number of deleted rows. This count
can be obtained by calling the ROW_COUNT() function (see
http://dev.mysql.com/doc/refman/5.1/en/information-functions.html). The
WHERE clause, if given, specifies the conditions that identify which
rows to delete. With no WHERE clause, all rows are deleted. If the
ORDER BY clause is specified, the rows are deleted in the order that is
specified. The LIMIT clause places a limit on the number of rows that
can be deleted.

For the multiple-table syntax, DELETE deletes from each tbl_name the
rows that satisfy the conditions. In this case, ORDER BY and LIMIT
cannot be used.

where_condition is an expression that evaluates to true for each row to
be deleted. It is specified as described in
http://dev.mysql.com/doc/refman/5.1/en/select.html.

Currently, you cannot delete from a table and select from the same
table in a subquery.

As stated, a DELETE statement with no WHERE clause deletes all rows. A
faster way to do this, when you do not need to know the number of
deleted rows, is to use TRUNCATE TABLE. However, within a transaction
or if you have a lock on the table, TRUNCATE TABLE cannot be used
whereas DELETE can. See [HELP TRUNCATE TABLE], and [HELP LOCK].

URL: http://dev.mysql.com/doc/refman/5.1/en/delete.html

