For me, 6. All of them were at low level jobs, however.
- Teenager working at a restaurant
2-4. Worked as a call center employee (non-manager)
5-6. Worked at a standardized testing office.
Had no effect on my job at all.
For me, 6 as well.
1-4 Teenager working at an amusement park, over the course of 3 summers.
5&6 Working in theatres.
The amusement park ones got a little awkward, but what teenage relationships don’t. Would have been awkward simply because everyone know everyone.
- I was working at a Pizza Hut call center and slept with one of the store managers. (we never actually worked together, I only met him because of a late night bowling outing we decided to do and a lot of the call center people knew him)
I don’t believe I would ever sleep with someone I actually worked directly with.
Just one. I was her manager.
It sort of fizzled out, and things were really awkward after that.
ETA: Wait, make that two. The second was technically my superior, but we never actually worked together. It ended badly.
Zero. 
None. But not for lack of trying…
One. We were both lifeguards at a water park. My god, he was hot. That was my first and only fuck-buddy situation, and we had a completely fun summer. Good times.
Only one. I worked as a pizza delivery guy, she worked as a waitress.
The silly girl ended up marrying me!
None.
Just one, though I use the term “coworker” loosely since we were both employed by the same company and worked in the same building (along with thousands of others). We met while working together in the call centre, but we had both moved on to other departments by the time we became an item.
Not that it’s a concern these days (seeing as I’m hitched and all)… but I would never ever date someone who worked in the same department, or that I’d have to see in a professional capacity on a regular basis. Too much possibility of my personal AND professional lives going to hell in a handbasket simultaneously.
All of them.
Does oral count?
Zilch. Zip. Zero. There are some I would consider if I was single, but since I’m not, it’s tricky. 
- My now ex-wife and I hooked up with the night manager for the Pizza place we worked.
Good times.
There have been a handful of ladies I wished, prayed, and tried with, but no success. All of them thought I was cute, and a good friend.
sigh
Zero.
<sigh> Yes, Mr. President.
Four, counting the one I married.
Five counting two I married, the first before I worked with her, in fact the day before.
Two. That’s not that many, considering that was over a couple of decades. Besides, where better to meet smart, attractive women than the babes of the corporate IT department? I’ll admit, one of them was my boss the first time I asked her out. She declined, but we dated after I transferred out of her group. Alas, she’s married to somebody else now. Either I did something wrong, or I failed to do something right, and she found a better man.
11 :o
Are you hiring? 