Oracle function that generate random number

In the oracle distribution, it doesn t exist any function that generate random numbers.
I would like to define this function.
This function would then allow me to retrieve a random row. Something who look like

Select random_function (pass_in_variables) from table_name.

Does anyone know or already programmed a plsql function who do this ?

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Dominique
dschoen_at_lysis.ch