I think what you're asking is whether Vol(salt) + Vol(water) = Vol(solution). The answer is no.
For sodium chloride and water, Vol(solution) < Vol(salt) + Vol(water). For other salts (e.g. lithium iodide) the opposite can occur. This absurdly long paper (it's paywalled, so go to a university library if you want to read it) gives data for the alkali metal halides.