add random SQL function

[jimexist]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

A challenge, to add random SQL function.

Describe the solution you'd like

select random();

Shall give a float64 in range [0, 1.0)

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.