Databases in the Wild
I keep backyard chickens so I thought that an interesting real world example of entity relationships would be the chicken keeping process. In the following diagram, we see that a caretaker provides water (which only comes in one type: the wet kind) and food, which may come in multiple types of corn, scratch, and chow pellets. Along with water, multiple types of food may be given to the chicken(s). Each chicken always has one and only one breed type, though there are a huge variety of possible breeds. Some chickens may lay multiple eggs (hens lay eggs, roosters don't). All eggs must have a color; typical egg colors are white, brown, and green. All eggs have one and only one fate: they are either cooked and eaten, given away for someone else to eat, or are broken before making it safely to the kitchen.