The files do not need to be in sort order. Matching is done by comparing the values of common variables. When there are many tables files the linking may be indirect. This means that all the files do not need to have the same key variables. Number Q4 Variable Social.
Security provides a direct link between the input file and the first table file.
Number provides a direct link between the first table file and the second table file. Thus there is an indirect link between the input file and the second table file. The resulting output file would have the following variables. Various optional identifiers specify the variables that are to be included in the output file. A template can be provided to specify which variables are to be included and their order in the output file.