[BookShop] 좋아요 API 구현 - count(), EXISTS

기본 LikesController.jsconst conn = require('../mariadb'); //db 모듈const {StatusCodes} = require('http-status-codes'); //status code 모듈const addLike = (req, res) => { // 좋아요 추가 const {id} = req.params; const {user_id} = req.body; let sql = "INSERT INTO likes(user_id, liked_book_id) VALUES (?, ?);"; let values = [user_id, id]; conn.query(sql, values, (err, results) => { ..