What is a captive portal?

There are many definitions out there which are explaining about captive portal like in TechTarget SearchMobileComputing, Answers.com, and Wikipedia. Still haven't got it? Well, have you found yourself connected in a public hotspot such as at the public venues, airport lounges, or hotel plaza? it's so common if we're going to browse to any pages using our favorite web browser we're forced to see a page to accept the Terms of Service (ToS) of the hotspot provider or submits username and password in order to be able to continue browse the web. Those kind of web pages are so called captive portal.

Ever wanted to do some update on multiple rows with different value or on different condition in a single SQL query? Usually, this can be done by executing some queries in a row as needed. But with MySQL we can do it in a single SQL query. How come?