酒屋 and 居酒屋 have slightly different meanings, according to what I have learned. 酒屋 would be liquor store; a store where you can go to buy bottled liquor or beer. 居酒屋 would be a kind of bar or restaurant that sells alcoholic beverages with small dishes of food.

Sakaya are shops for Osake. Izakaya are the place for drinking Osake in night time.

酒屋 is wine or liquor shop, so you can buy it. 居酒屋 is a cheep pub. We can drink and eat in it. But we can't buy liquor. long time ago, we could drink in 酒屋 like one shot bar.