SAS Certified Professional Prep Guide

Generating a Cartesian Product

The most basic type of join combines data from two tables that are specified in the FROM clause of a SELECT statement. When you specify multiple tables in the FROM clause but do not include a WHERE statement to subset data, PROC SQL returns the Cartesian product of the tables. In a Cartesian product, each row in the first table is combined with every row in the second table. The following example illustrates a Cartesian product where table One and table Two are joined using a FROM clause.

proc sql;
   select *;
      from certadv.one, certadv.two
;
quit;

The output shown below displays all possible combinations of each row in table One with all rows in table Two. Note that each table has a column named X, and both ...