You can use SQL to join tables in JMP using Query (Query(<<dt1|Table(dt1, alias1)>, ..., <dtN, aliasN)>>, <private | invisible>, <scalar>, sqlStatement...). Part of example from scripting index:
Names Default To Here(1);
// Using aliases, performing a join
dtSAT = Open("$SAMPLE_DATA/SATByYear.jmp", Invisible);
dtUS = Open("$SAMPLE_DATA/US Demographics.jmp", Invisible);
Query(
Table(dtSAT, "t1"),
Table(dtUS, "t2"),
"\[SELECT t1.State, t1."SAT Math", t2."College Degrees",
t2."Eighth Grade Math"
FROM t1
LEFT OUTER JOIN t2
ON t1.State = t2.State
WHERE t1.'SAT Math' > 550;
]\"
);
-Jarmo