07-09-2017 08:20 AM
in1 is just a name of something. It's probably a variable name, but could be anything that would be named within a SAS program (a variable, a data set , an array). So its meaning depends on the context within the program.
in1.a also depends on context. In most cases, it is the data set A, stored within the library IN1. But within SQL, it is the variable A stored within the data set IN1. There may be other possibilities, but those are the main ones.
in1..a doesn't exist in SAS.
07-09-2017 10:10 AM
Just out of curiosity: where did you get the notion that there is such a thing as "in1..a" in SAS?
07-09-2017 10:14 AM - edited 07-09-2017 10:15 AM
The place in SAS where you might see double periods like that would be when using macro variables to generate a string that needs to have a period in it. For example if you had a macro variable than contained the library name and you wanted to generate a reference to particual dataset in that library.
libname mydata 'my path'; %let libref=mydata; proc print data=&libref..myds; run;
The first period is used by the macro processor to indicate the end of the macro variable name. So the result of "&libref..myds" is the string "mydata.myds".