digraph sample {
  graph[overlap=false, splines=true]

  "category" [shape=record, label="{category|name\l}"]
  "customer" [shape=record, label="{customer|name\lphone_number\l}"]
  "order" [shape=record, label="{order|customerID(FK)\lproductID(FK)\lorder_num\l}"]
  "product" [shape=record, label="{product|categoryID(FK)\lname\lamount\ltax\lproduct_div\l}"]

  "category" -> "product" [arrowtail=none arrowhead=dot headlabel="n" taillabel="1"]
  "customer" -> "order" [arrowtail=none arrowhead=dot headlabel="n" taillabel="1"]
  "product" -> "order" [arrowtail=none arrowhead=dot headlabel="n" taillabel="1"]

}