SUPPLIER Table $($S#$,$ SNAME, STATUS, CITY$)$ PART Table $($P#$,$ PNAME, COLOR, WEIGHT$)$

P# PNAME COLOR WEIGHT

S# SNAME STATUS CITY $------------------$

$---------------------------$ P$1$ Nut Red $12$

S$1$ Smith $20$ London P$2$ Bolt Green $17$

S$2$ Jones $10$ Paris P$3$ Screw Blue $17$

S$3$ Blake $30$ Paris P$4$ Screw Red $14$

S$4$ Clark $20$ London P$5$ Cam Blue $12$

S$5$ Adams $30$ Athens P$6$ Cog Red $19$

SHIPMENT Table $($S#$,$ P#$,$ QTY$)$

S# P# QTY

$--------------$

S$1$ P$1300$

S$1$ P$2200$

S$1$ P$3400$

S$1$ P$4200$

S$1$ P$5100$

S$1$ P$6100$

S$2$ P$1300$

S$2$ P$2400$

S$3$ P$2200$

S$4$ P$2200$

S$4$ P$4300$

S$4$ P$54006.$ Describe the nature of the referential integrity constraint$($s$)$ that involve the PART and SHIPMENT tables.