The dbjoin command joins the specified cursors and returns a
cursor handle that can be used to iterate through the joined {key data}
pairs. The returned cursor handle is bound to a Tcl command of the form
dbN.cX, where X is an integer starting at 0 (e.g., db0.c0 and
db0.c1). It is through this Tcl command that the script accesses the
cursor methods.
The returned join cursor has limited cursor functionality and only the
dbcget and dbcclose commands will succeed.
See Logical join for more information on
the underlying requirements for joining.
In a transaction protected environment, all of the cursors listed must
have been created within the same transaction.