When you are developing queries against large tables, you can reduce the amount of time that it takes for the queries to run by reducing the number of rows that PROC SQL processes. Subsetting the tables with WHERE clauses is one way to do this. Using the INOBS= and OUTOBS= options in PROC SQL is another way.

You already know that you can use the OUTOBS= option to restrict the number of rows that PROC SQL displays or writes to a table. However, the OUTOBS= option does not restrict the rows that are read. The INOBS= option restricts the number of rows that PROC SQL takes as input from any single source. The INOBS= option is similar to the SAS system option OBS= and is useful for debugging queries on large tables.

In the following PROC SQL set operation, INOBS=5 is specified. As indicated in the log, only five rows from each source table, Sasuser.Mechanicslevel1 and Sasuser.Mechanicslevel2, are used. The resulting table contains 10 rows.

proc sql inobs=5;
   select *
      from sasuser.mechanicslevel1
   outer union corr
   select *
      from sasuser.mechanicslevel2;

183   proc sql inobs=5;
184     select *
185        from sasuser.mechanicslevel1
186     outer union corr
187     select *
188        from sasuser.mechanicslevel2;

WARNING: Only 5 records were read from SASUSER.MECHANICSLEVEL1
         due to INOBS= option.
WARNING: Only 5 records were read from SASUSER.MECHANICSLEVEL2
         due to INOBS= option.