Conditional merge SAS PROC SQL - sql

Question

In my original code, I want to merge several data bases:
%let theft=1;
proc sql;
create table NewTable as
Select *
From
dtm_sitecom.FactSitecAllCriteria SITEC
left join dtm_sitecom.FactClaimLastVersion FactClaimLastVersion
on FactClaimLastVersion.ClaimId = Sitec.ClaimId
/*Condition 1 here*/
/*If &Theft=1 then*/
left join dtm_sitecom.DimClaimState DimClaimState
on DimClaimState.ClaimStateKey = FactClaimLastVersion.ClaimStateKey
/*Condition 2 here*/
/*else if &Theft = 0 then*/
left JOIN dtm_sitecom.DimGeoRisk dgr
ON dgr.GeoRiskKey = SITEC.GeoRiskKey;
quit;
On the upgraded version, I want to add some conditions (/Condition 1/ and /Condition 2/ in the code) such as, if the value of the variable Theft=1 then do the merge with the talbe dtm_sitecom.DimClaimState, otherwise do the merge with the other table. I tried the code as if there is no comment sign around the if, but it didn't work because of the wrong syntax. Is there any SAS syntax allowing me to do that?

Answer 1

If you are joining on a variable in the data, you can include that in the on statement:
data class_attach_m;
set sashelp.class;
attach_var='M';
run;
data class_attach_f;
set sashelp.class;
attach_var='F';
run;
proc sql;
create table class as
select class.*, coalescec(class_attach_m.attach_var,class_attach_f.attach_var) as attach_var from sashelp.class
left join class_attach_m
on class.name = class_attach_m.name
and class.sex='M'
left join class_attach_f
on class.name = class_attach_f.name
and class.sex='F'
;
quit;
coalescec (or coalesce for numerics) combines the two brought-in fields.
If you are using macro variables to control which you run, though, you need to be running this in a macro; if you're in a macro context, you can use %if to control what is executed.
For example, using the previous example - and I use a macro parameter not a %let as that's the right way to do it, though you can define that parameter using %let earlier and use it for the parameter call:
%macro attach_which(attach_m=M);
proc sql;
create table class as
select class.*, attach_var from sashelp.class
%if &attach_m=M %then %do;
left join class_attach_m
on class.name = class_attach_m.name
%end;
%else %do;
left join class_attach_f
on class.name = class_attach_f.name
%end;
;
quit;
%mend attach_which;
%attach_which(attach_m=M);