Changing Data and Structure - Mastering phpMyAdmin 3.4 for Effective MySQL Management - page 98

The actual DELETE statement will use whatever information is needed to ensure the
deletion of only the intended row. In our case, a primary key had been deined and
was used in the WHERE clause. In the absence of a primary key, a longer WHERE clause
will be generated based on the value of each column. The generated WHERE clause
might even prevent the correct execution of the DELETE operation, especially if there
are TEXT or BLOB column types. This is because the HTTP transaction, used to send
the query to the web server, may be limited in length by the browser or the server.
This is another reason why deining a primary key is strongly recommended.
Deleting multiple rows
Let us say we examine a page of rows and decide that some rows have to be destroyed.
Instead of deleting them one-by-one with the Delete link or icon and as sometimes
the decision to delete must be made while examining a group of rows, there are
checkboxes beside rows in Table view mode as shown in the following screenshot:
These are used with the Delete icon in the With selected menu. A confirmation
screen appears listing all the rows that are about to be deleted.
Deleting all of the rows in a table
To completely erase all the rows in a table (leaving its structure intact), we first
display the database Structure page by selecting the related database from the
navigation panel. We then use the Empty icon or link located on the same line as the
table we want to empty, shown as follows: