Mongodb数据库遍历 / 网络研习社#85

in hive-180932 •  last year 

mongodb.jpg

https://www.mongodb.com/

Mongodb是个简单易用、拓展性极强的数据库。对它的查询和遍历说不上难,但也有些技巧在的。

条件查询

//增加查找条件
or() :添加限制条件
limit(1) :查看几个
sort() :排序  
skip():跳过几个
User.find()//查询全部
  .or([{gender:2}])//查询gender为2的数据
  .sort({_id:'desc'})//倒序排列数据, 或sort({_id: -1}),asc正序  
  .limit(2)//展示两条
  .skip(2)//跳过前两个

eg:
let images = await User
     .find({user_id: req.user_id})
     .sort({_id:'desc'})
     .limit(50)

对数据库遍历

// nodejs端
//查询用户
app.get('/getusers/:skip', async (req, res) => {
  try {
    let limit = 5
    let skip = req.params.skip
    // 主要是通过limit和skip来进行遍历
    // limit 和 skip 要保持一致
    let users= await User
      .find()
      .sort({_id:'desc'})
      .limit(limit)
      .skip(skip)
    res.status(200).send({
      users
    })

  } catch (err) {
      console.error(556, err)
      res.status(500).send('Something went wrong');
  }
})

// nuxt前端
let skip = 5
let skipNum = ref(0)
//获取用户
const getHistory = async () => { 
  const getOption = {
    method: "GET",
    baseURL
  }
  let { data,  error } =  await useFetch('/getusers/0', getOption)
  console.log(668, data.value.users)
}

if(process.client){
  getHistory()
}

const more = async () => {
  console.log(563, "skipNum", skipNum.value)
  const getOption = {
    method: "GET",
    baseURL
  }
  skipNum.value += skip
  let { data,  error } =  await useFetch('/getusers/'+skipNum.value, getOption)
  if(error.value) {
    message.error("失败!\n"+error.value.data, { duration: 5e3 })
    return
  }
  if(data.value.users.length < skip){
    console.log("没有更多数据了!")
    moreFlag.value = false
  }
}

这个遍历有点像接力赛,查完一段再查下一段。通过limit和skip来完成一段段的查询,效果还是很完美的。

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