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In SAS, you can perform a left join by using the proc sql join statement with the left join keyword. The left join statement allows you to keep all of the rows from the left table, and match them with the rows from the right table if they exist. If no match is found, then the right table column values will be listed as missing. You must also specify the matching condition in the on clause for the join statement.
You can use the following basic syntax to perform a left join with two datasets in SAS:
proc sql;
create table final_table as
select * from data1 as x left join data2 as y
on x.ID = y.ID;
quit;
The following example shows how to use this syntax in practice.
Related:
Example: Left Join in SAS
Suppose we have the following two datasets in SAS:
/*create datasets*/
data data1;
input team $ points;
datalines;
Mavs 99
Spurs 93
Rockets 88
Thunder 91
Warriors 104
Cavs 93
Grizzlies 90
Hawks 91
;
run;
data data2;
input team $ rebounds;
datalines;
Mavs 21
Spurs 18
Rockets 22
Warriors 27
Cavs 15
Hawks 29
;
run;
/*view datasets*/
proc print data=data1;
proc print data=data2;
Notice that the two datasets share one variable in common: team.
We will use the following syntax to perform a left join and create a new dataset that contains every row from data1 and only the rows from data2 that match a team name in data1:
/*perform left join*/
proc sql;
create table final_table as
select * from data1 as x left join data2 as y
on x.team = y.team;
quit;
/*view results of left join*/
proc print data=final_table;
The resulting dataset contains every original team from data1, but the only teams that have values for the rebounds column are the ones that also appeared in data2.
The following tutorials explain how to perform other common tasks in SAS: