arguments of the functon for VPD.

Hi all,

   Recently,I have been studing the Virtual Private Database in oracle,when I tried to write the function that will return predicate following some examples,I found all the example functions(perhaps there are exectpions that I have not found) own two and only two arguments, and the two arguments are not used in the function body.    My question is: Can the function have other arguments other than the two? Can the arguments be used in the function body?And is there any material of specification for the VPD function?

   Thank you in advance.

  xiaoyan.

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