When you need to select data from multiple tables and combine the tables horizontally (side by side), PROC SQL can be an efficient alternative to other SAS procedures or the DATA step. You can use a PROC SQL join to combine tables horizontally:

proc sql;
   select *
      from a, b
      where a.x=b.x;

A PROC SQL join is a query that specifies multiple tables and/or views to be combined and, typically, specifies the conditions on which rows are matched and returned in the result set.

You should already be familiar with the basics of using PROC SQL to join tables. In this chapter, you take a more in-depth look at joining tables.