https://blog.gongquiz.com/2023/03/02/%eb%8b%a4%ec%9d%8c-%ec%a4%91-%ec%a3%bc%ec%96%b4%ec%a7%84-customer-%ed%85%8c%ec%9d%b4%eb%b8%94%ec%9d%84-%ec%b0%b8%ec%a1%b0%ed%95%98%ec%97%ac-%ec%95%84%eb%9e%98%ec%9d%98-sql%eb%ac%b8%ec%9d%84/