Light switch only has live wire is this right?
is this right?


No.

Firstly, Blue-Tack is not an acceptable way of insulating a loose wire. 

Secondly, the blue wire should be connected to the switch. Otherwise the switch has no purpose.

This is sufficiently strange that I'd turn off the breaker for this circuit, open up the outdoor light, note the connections, disconnect the wires and check continuity back to the blue wire you show in the picture. It may be that things are not wired as you think they are - it is important to be sure before connecting the blue wire and potentially energising some unknown device or fitting. It might be that the blue wire was disconnected because of a fault elsewhere that constitutes a potential safety hazard.



Your photo looks like a typical light-switch in a UK kitchen built or rewired in the last decade or so.

UK lights are usually wired like this:



There should be tape on both ends of the blue wire from the switch to indicate it is live (or switched live) and not neutral. Normally red tape would be used. In your case white tape seems to be used.

Often the blue and brown wires from the switch are connected the other way around at the junction-box (or ceiling rose) for the light. I.e. blue (with tape) to position 2, brown to position 3.