demo database is not installing

i am installing nav 2016 i choose custom option and installed client,server,but while installing database component it install successfully
but demo database is not installing it gives me following error

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Setup

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Some components are missing parameters and cannot be installed.

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OK

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Note that SQL server database component: SQL server field ,sql server instance field ,sql database field is Blank and non editable while typing on that field
is their any solution thanks in advance