Returns the error text from the last MySQL function, or
'' (the empty string) if no error
occurred.
Errors coming back from the MySQL database backend no
longer issue warnings. Instead, use
mysql_error() to retrieve the error text. Note that this
function only returns the error text from the most recently
executed MySQL function (not including
mysql_error() and mysql_errno()), so if you want to
use it, make sure you check the value before calling another
MySQL function.
注: If the optional argument is specified the given link is used to retrieve the error message. If not, the last opened link is used.
See also: mysql_errno()