how to verify username and password enter to a textbox with those in database?

[POla]

Let say user need to key in username and password to login a form. How can i verify the username and password with those valid username and password sotred in a database?

[Marc G]

How can we know this?
It all depends on what database you are using.

One thing though, please store passwords encrypted with a one-way encryption scheme in your database. One-way encryption means that you cannot ge the original password back from the encrypted one.
To check for a password, you simply one-way encrypt the entered password and check that value with the values in the database.