SAS - merge with formatted data

SAS_merge_groupformat.sas

*This example demonstrates how you can merge data with a formatted variable and not have to create a new variable;

data stocks_A;
set sashelp.stocks;
where stock='IBM';
format date yymmn6.;
*keep only relevant variables for testing;
keep date open;

*rename to identify source;
rename open=OpenA;
run;

data stocks_B;
set sashelp.stocks;
where stock='IBM';
*dates are not the same now in each data set;
DATE = DATE + 1;
format date yymmn6.;

*keep only relevant variables for testing;
keep date open;

*rename to identify source;
rename open=OpenB;
run;

proc sort data=stocks_A; by date;
proc sort data=stocks_B; by date;
run;

*with group format;
data merged;
merge stocks_A stocks_B;
by date groupformat;
format date yymmn6.;
run;

*without group format;
data merged_WRONG;
merge stocks_A stocks_B;
by date;
format date yymmn6.;
run;