You also need to clarify "approach" because the way women and men think about approaching are two different things. For a woman, being within like 10 ft of a guy is an approach and it is up to the guy to sense it and make things happen.
If you mean the woman actually comes up to you and starts talking or something that is a different story. The last time I had a woman "approach" me was at a bar about a month ago. She sat right next to me - there were many other seats she could've taken and I was sitting at the end so it wasn't even really the best place to sit at a bar if that makes sense (the tv was infront and I just wanted to see the World Cup game). I know she "approached" me because I talked to her and she was into it, defenses were down etc. you can just tell when a woman likes you and is talking to you.
The last time I have actually had a woman flat out boldly approach me was like a few days before Halloween. There was a Halloween themed pub crawl that day and I had stopped into this lounge with a friend of mine. My Michael Myers dressed ass (lol, didn't have the mask on, just the coveralls) was sitting at a table and I was having a mixed drink when not far from me there was this group of what I think were friends, they were hanging in the dance floor part of the lounge. One of them came up to me and asked if I could take a photo of them and I did. Afterwards when I gave the girl here phone back and was about to go back to my table the girl said you have to take a picture with my friends, can you be in the group photo? And I thought well this doesn't usually happen and I took one, then I started to talk to with a couple of the girls a bit. They were very young like 20, so too young for me, but I was pretty sure one of them at least liked me. This should give you an idea of how they operate; they are never direct and usually talk to you on the grounds of some other purpose - you have to be quick to decode the situation.