Reading Multiple Sybase Tables

SAS opens multiple Sybase tables for simultaneous reading in these situations:

When you are using PROC COMPARE. Here is an example:
```
proc compare base=syb.data1 compare=syb.data2; 
```
When you are running an SCL program that reads from more than one Sybase table simultaneously.

When you are joining Sybase tables in SAS—namely, when implicit pass-through is not used (DIRECT_SQL=NO). Here are four examples:

proc sql ;
   select * from syb.table1, syb.table2 where table1.x=table2.x;

proc sql;
   select * from syb.table1 where table1.x = (select x from syb.table2
   where y = 33);

proc sql;
   select empname from syb.employee where empyears > all (select empyears
   from syb.employee where emptitle = 'salesrep');
proc sql ;
   create view myview as
      select * from employee where empyears > all (select empyears from
      syb.employee where emptitle = 'salesrep');
proc print data=myview ;

To read two or more Sybase tables simultaneously, you must specify either the LIBNAME option CONNECTION=UNIQUE or the LIBNAME option READLOCK_TYPE=PAGE. Because READLOCK_TYPE=PAGE can degrade performance, it is generally recommended that you use CONNECTION=UNIQUE (unless there is a concern about the number of connections that are opened on the database).