Hello,
On an MP5SD,
the suppressor is integral correct?

therefore, can it be removed at all?

and can they be fired in non suppressed mode?

is it like a switch?

sorry I love those guns but have no idea how they do their thing.

also if it does switch on/off, is there one that someone does for the AR? like knights?

Yes, it can be removed for cleaning. It simply and easily unscrews.

As to shooting it "without," I imagine it would go "bang" and probably even cycle, but I wouldn't recommend it. The MP5SD's barrel is ported in all directions about 4"-8" or so from the chamber. This is to bleed a few hundred feet per second or so from the muzzle velocity of normal 9mm ammo, so that the rounds are subsonic when they exit the muzzle and do not have the loud accompanying "crack" that normal supersonic 9mm rounds produce. Because of this, firing the weapon without the suppressor would likely lead to nasty jets of hot gas burning your support hand and arm, and maybe even your face. Probably not a good idea.

The barrel is ported near the chamber end. It is removable for cleaning but I would advise against firing a radial ported barrel without it's can on. The suppressor cannot be "switched off" they fill up with gas and become less efficient; ie noisier.
Edit: Not known for my quick draw

thanks y'all I has always wondered that.

From an operational flexibility standpoint, the MP5N model is probably a better bet.  It's got a removable suppressor, telescoping stock and simple single, full auto and safe selector. You can use +p+ ammo without the suppressor and subsonic with it.  You can also mount a suppressor on the MP5/10 model and get trigger kits and the rest to mimick the MP5N, plus you get the power of the 10mm Auto cartridge, which is a HUGE step up from the 9mm NATO.

In real world use, the SMG is being eclipsed by the M4 carbine.  Strange as it seems, the 5.56mm round fired from the M4 is less prone to overpenetration of both bodies and building materials than the 9mm round thanks to violent fragmentation at CQB ranges.  You can also suppress the M4 nicely.  It won't be as quiet as the MP5SD series which is scary quiet, but it'll definitely make shooting the 5.56mm NATO round a lot more comfortable in closed quarters.