nodeJs中实现连表查询
router.post('/getOrder', async function(req, res, next) {
let userId = req.body.phone;
let sql = 'select * from orders where userId=?';
let orders = await new Promise((resolve, reject) => {
connection.query(sql, [userId], function(error, result) {
if (error) {
reject(error);
} else {
resolve(result);
}
});
});
for (let i = 0; i < orders.length; i++) {
let foodId = orders[i].foodId;
let foodSql = 'select * from food where id=?';
let food = await new Promise((resolve, reject) => {
connection.query(foodSql, [foodId], function(error, result) {
if (error) {
reject(error);
} else {
resolve(result);
}
});
});
orders[i].foodList = food; // 将foodList数组添加到对应的order对象中
}
console.log('Orders with Food List:', orders);
res.send({
code: 200,
data: {
data: orders
}
});
});
异步操作
创建一个Promise对象:
let myPromise = new Promise((resolve, reject) => {
// 异步操作,比如数据库查询、文件读取等
if (/* 操作成功 */) {
resolve('操作成功,返回结果');
} else {
reject('操作失败,返回错误信息');
}
});
myPromise.then((result) => {
// 当Promise状态为fulfilled时调用,result为操作成功的结果
console.log(result);
}).catch((error) => {
// 当Promise状态为rejected时调用,error为操作失败的错误信息
console.log(error);
});
let promise1 = Promise.resolve(1);
let promise2 = Promise.resolve(2);
Promise.all([promise1, promise2])
.then((results) => {
console.log(results); // [1, 2]
})
.catch((error) => {
console.log(error);
});
let promise1 = new Promise((resolve) => setTimeout(resolve, 500, 'one'));
let promise2 = new Promise((resolve) => setTimeout(resolve, 100, 'two'));
Promise.race([promise1, promise2])
.then((value) => {
console.log(value); // 'two'
});
🎉写在最后
🍻伙伴们,如果你已经看到了这里,觉得这篇文章有帮助到你的话不妨点赞👍或 Star ✨支持一下哦!手动码字,如有错误,欢迎在评论区指正💬~
你的支持就是我更新的最大动力💪~