Sequelize how to check if entry exists in database

问题

I need to check if entry with specific ID exists in the database using Sequelize in Node.js

  function isIdUnique (id) {
    db.Profile.count({ where: { id: id } })
      .then(count => {
        if (count != 0) {
          return false;
        }
        return true;
      });
  }

I call this function in an if statement but the result is always undefined

if(isIdUnique(id)){...}

回答1:

Update: see the answer which suggests using findOne() below. I personally prefer; this answer though describes an alternative approach.

You are not returning from the isIdUnique function:

function isIdUnique (id) {
    return db.Profile.count({ where: { id: id } })
      .then(count => {
        if (count != 0) {
          return false;
        }
        return true;
    });
}

isIdUnique(id).then(isUnique => {
    if (isUnique) {
        // ...
    }
});

回答2:

I don't prefer using count to check for record existence. Suppose you have similarity for hundred in million records why to count them all if you want just to get boolean value, true if exists false if not?

findOne will get the job done at the first value when there's matching.

const isIdUnique = id =>
  db.Profile.findOne({ where: { id} })
    .then(token => token !== null)
    .then(isUnique => isUnique);

回答3:

You can count and find.

    Project
  .findAndCountAll({
     where: {
        title: {
          [Op.like]: 'foo%'
        }
     },
     offset: 10,
     limit: 2
  })
  .then(result => {
    console.log(result.count);
    console.log(result.rows);
  });

Doc link, v5 Beta Release

回答4:

As Sequelize is designed around promises anyway, alecxe's answer probably makes most sense, but for the sake of offering an alternative, you can also pass in a callback:

function isIdUnique (id, done) {
    db.Profile.count({ where: { id: id } })
      .then(count => {
        done(count == 0);
      });
  }
}

isIdUnique(id, function(isUnique) {
  if (isUnique) {
    // stuff
  }
});

回答5:

I found the answer by @alecxe to be unreliable in some instances, so I tweaked the logic:

function isIdUnique (id, done) {
  db.Profile.count({ where: { id: id } })
  .then(count => {
    return (count > 0) ? true : false
  });
}

来源：https://stackoverflow.com/questions/36480587/sequelize-how-to-check-if-entry-exists-in-database

标签

javascript

node.js

sequelize.js