PHP MySQL infoga multimensional associativ arraybyggningsfråga från arraynycklar

T.ex.:

core_table
id* unit quantity description
 1  car         3 Description 1
 2  bike       74 Description 2

adjunct_table
core_id* meta_key* meta_value
      1        47  Description of key n.47 first row
      2        47  Description of key n.47 second row

* = (component of) PRIMARY KEY