SET CONNECTION
The SET CONNECTION statement activates a specified connection.
General format
EXEC SQL [ AT Database ]
 
  SET CONNECTION { Connection-name }
 
END-EXEC
Syntax rules
1. Connection-Name is a host variable or Nonnumeric Literal, as defined in the Definitions section of the Preface of this document.
General rules
1. When two or more connections are opened you can choose the active connection using the Connection-Name parameter.
2. Database identifies the active connection that will execute the query and must be previously defined using a Format 4 DECLARE statement.
Examples
Switch from one connection to another when having one connection to an Oracle DB and other to a MySQL DB
if db-to-use = ora-db
   exec sql
     set connection ora-conn-1
   end-exec
else
   exec sql
     set connection mysql-conn-2
   end-exec
end-if