If you got a Photo with Banding already in it because likely someone else f*cked up you can take advantage of the fact, that banding only happened in areas of the Image with gradients.
To do that, just select either the part with the banding in it or without it. Personally, I like t use the Quick Selection Tool for something like that.
If you are Donne, Press Ctrl/command + J to Copy the selected on a new Layer
Hold Ctrl/command and click on the new Created Layer, to get the same selection again. Now select the Original Layer, Click on Select>Inverse to inverse your selection and Press Ctrl/command + J again.
Now you have the Original Layer, a Layer with the Part without banding, The Part with Banding and the Original Layer. If not, put it in this order.
Now select the Layer with the Banding and Click on Filter>Blur>Gaussian Blur and set it strong enough to completely remove the banding.
After that, hit on okay.