Update multiple rows in a table from another table when condition exists

Question

I have two tables.

Table1 contains companies whose locations are georeferenced with lat/lng coordinates in a column called the_geom

Answer 1

Assuming that by

insert "the_geom" lat/lng values

you actually mean to update existing rows in table2:

UPDATE table2 t2
SET    the_geom = t1.the_geom
FROM   table1 t1
WHERE  t2.address = t1.address
AND    t2.the_geom IS DISTINCT FROM t1.the_geom; -- avoid empty updates

Also assuming that the address column has UNIQUE values.
Details about UPDATE in the excellent manual here.