I'm just a little confused about the SSDT version numbers. Microsoft currently lists SSDT 17.4 for use in VS 2015, but after I install it, VS 2015 Help About says I have SSDT version 14. Control Panel also says I have version 14 installed (and some older ones), but with the current install date. Also I see "Prerequisites for SSDT" up to version 13,, but not for version 14 (is this just because I don't have SQL Server 2017 LocalDB?
Of course SQL Server version 14 is 2017 - so am I missing something, or is this just a dual numbering scheme from MS?