If you are using SQL SERVER 2017 then you have overwrite SIF/Sitecore.Commerce.1.0.1748\Modules\DeployCommerceDatabase\DeployCommerceDatabase.psm1 file .
download the file from https://gitlab.com/viet.hoang/workshop/raw/master/Scripts%20for%20Sitecore%20Commerce%20901/DeployCommerceDatabase.psm1 and replace it with file mentioned above.
Please make sure that you do not replace the file, you have to copy the contents from the new file (excluding the signature part) and replace it in the new file(excluding the signature ) other wise the signature will not match and the installation will not work
Now, start the installation again
Sitecore Genie - Himanshu Agarwal's blog 