Programming language generations 4th? 5th? are there more?

Well as classified in school and collage days popular programming languages (C# , java , C++) are all 3rd generation languages ( with higher level of abstraction from the machines physical parts)

This keeps assembly at 2nd and machine language as 1st generations languages.

Initially I was thinking SQL should be considered 4th Gen Language cause it is more abstract and far away from details of looping and more descriptive .

just now i found out there are 4th Generation and 5th Geniration languages but based on what any programming language or technology is now categorized on to be 4th or 5th ?? is there 6th or 7th generation languages as well ??