How can prevent duplicate record in portal?

[santosh]

how can i prevent duplicate record in portal?

if a data is exist in the portal row then in other row the same data should not be entered again.

how can i do it?

[IdealData]

Portal or not, it does not matter. You must decide first what are the criteria that determines that any given record is a duplicate of another. When you can do that then you can set the validation criteria to be unique on the relevant field(s).