How many compounds are there in a salty water?

This is difficult to answer as salts in solution recombine with each other forming other salts.

For example if you dissolved the two salts, sodium chloride and potassium iodide in water the solution would contain all of these compounds:

1. water
2. sodium chloride
3. potassium iodide
4. sodium iodide
5. potassium chloride

If only one salt was dissolved the number of compounds is always just two: water and that salt. But the more salts dissolved the much more ways they can recombine in solution to produce additional compounds.