//1.insert操作
let insertSql = 'insert into User(username,password,name,gender,age) values (?,?,?,?,?)';let insertParams = [username, password, name, gender, age];mysqlConnection.query(insertSql, insertParams, function (error, results, fields) { if (error) throw error; return results;});//2.select操作(我自己测试的时候发现,字符串类型的列,要给参数额外增加引号,否则会被当做数字类型或列名来进行处理)let selectSql = 'select id from User where username = \''.concat(username, '\' and password = \'', password, '\'');mysqlConnection.query(selectSql, function (error, results, fields) { if(error) throw error; return results;});//3.delete操作let deleteSql = 'delete from user where id = \''.concat(id, '\'');mysqlConnection.query(deleteSql, function (error, results, fields) { if (error) throw error; return results;});//4.update操作let updateSql = 'update User set age = 30 where id = \''.concat(id, '\'');mysqlConnection.query(updateSql, function (error, results, fields) { if (error) throw error; return results;});