Renaming Variables in HASH merge in SAS - hash

Question

I was trying to learn HASH joins in SAS but I am stuck on the case where I have multiple tables with the same variable names (not for the key, that's okay, but the other variables)
I want to join tables A, B and C each with two variables Key and Dat. The name Key and Dat is common in all three
This syntax works for me if I rename Dat in all three tables before hand to DAT_A, DAT_B, DAT_C but that defeats the purpose since I have to call all three tables which takes time
This code works:
data merged(keep=KEY DAT_A DAT_B DAT_C);
if 0 then
set A B C;
if _N_ = 1 then
do;
declare hash A(dataset:'A');
A.defineKey('KEY');
A.defineData('DAT_A');
A.defineDone();
declare hash B(dataset:'B');
B.defineKey('KEY');
B.defineData('DAT_B');
B.defineDone();
end;
set C;
if A.find(key:KEY) = 0 and B.find(key:KEY) = 0 then
output; run;
Its mentioned on the SAS website that you can specify options in data in the hash declare so I thought this might work
data merged(keep=KEY DAT_A DAT_B DAT_C DAT);
if 0 then
set A B C;
if _N_ = 1 then
do;
declare hash A(dataset:'A (rename=(DAT=DAT_A))');
A.defineKey('KEY');
A.defineData('DAT_A');
A.defineDone();
declare hash B(dataset:'B (rename=(DAT=DAT_B))');
B.defineKey('KEY');
B.defineData('DAT_B');
B.defineDone();
end;
set C (rename=(DAT=DAT_C));
if A.find(key:KEY) = 0 and B.find(key:KEY) = 0 then
output; run;
However running this gives the following error
ERROR: Variable DAT is not on file WORK.A.
ERROR: Hash data set load failed at line 33 column 4.
ERROR: DATA STEP Component Object failure. Aborted during the EXECUTION phase.
Does anyone have any ideas
Thanks a lot

Answer 1

You are including DAT in the keep= dataset option on your output dataset. But your data step doesn't have the variable DAT anymore. You have renamed all copies of it.
Your error message about dataset A not having DAT is probably because of your earlier attempts to rename the variable to DAT_A.
Here is example using SASHELP.CLASS.
data merged ;
keep NAME AGE_A AGE_B AGE_C ;
if 0 then set
sashelp.class(rename=(AGE=AGE_A))
sashelp.class(rename=(AGE=AGE_B))
sashelp.class(rename=(AGE=AGE_C))
;
if _N_ = 1 then do;
declare hash A(dataset:'sashelp.class (rename=(AGE=AGE_A) where=(age_a ne 14))');
A.defineKey('NAME');
A.defineData('AGE_A');
A.defineDone();
declare hash B(dataset:'sashelp.class (rename=(AGE=AGE_B) where=(age_b ne 13))');
B.defineKey('NAME');
B.defineData('AGE_B');
B.defineDone();
end;
set sashelp.class (rename=(AGE=AGE_C));
/* if A.find(key:NAME) = 0 and B.find(key:NAME) = 0 then output; */
if A.find(key:NAME) then call missing(age_a);
if B.find(key:NAME) then call missing(age_b);
run;