db_schema.puml

@startuml

!define table(x) class x << (T,#FFAAAA) >>
!define primary_key(x) <u>x</u>
hide methods

table(CUSTOMER){
    + primary_key(CUSTOMER_KEY)
    + FIO
    + AGE
}
table(PURCHASE) {
    + primary_key(PURCHASE_KEY)
    + PRODUCT_KEY
    + CUSTOMER_KEY
    + QTY
    + DATE
}
table(PRODUCT) {
    + primary_key(PRODUCT_KEY)
    + CATEGORY_KEY
    + NAME
    + PRICE
}
table(PRODUCT_CATEGORY) {
    + primary_key(CATEGORY_KEY)
    + CATEGORY
}

CUSTOMER::CUSTOMER_KEY "1" --> "∞" PURCHASE::CUSTOMER_KEY
PRODUCT::PRODUCT_KEY "1" --> "∞" PURCHASE::PRODUCT_KEY
PRODUCT_CATEGORY::CATEGORY_KEY "1" --> "∞" PRODUCT::CATEGORY_KEY

@enduml