SQL-99 does not allow to delete data in a table when using JOINS. The reasons for this are quite obscure. Maybe it was considered too complicated to implement. Therefore for safety reasons it was not part of the standard.
As a result, MySQL implemented this feature and PostgreSQL rejected it.
The following query works under MySQL but fails under PostgreSQL:
DELETE h FROM history AS h INNER JOIN term_node AS tn ON (h.nid = tn.nid) INNER JOIN term_data AS td ON (td.tid = tn.tid) WHERE h.uid = 2067 AND td.vid = 2