如何使用特定字段Firebase获取数据？

Question

I have structure like this :

{ 
2018-02-27: {
-L6MTxsb_aJoKhMNA6X0 : {
comment: ...
created: ...
price : ...
}
-L6MTxsb_aJoKhCNA6X0 : {
comment: ...
created: ...
price : ...
employeeId: ...
}
}
2018-02-27: {
-L6MTxsb_aJoKhMNA6X0 : {
comment: ...
created: ...
price : ...
}
-L6MTxsb_aJoKhCNA6X0 : {
comment: ...
created: ...
price : ...
employeeId: ...
}
}

How to get only that objects which have employeeId key

I need to pass parametr to function and get values which equals to this parametr I tried this:

export const loadForEmployee = async employeeId => {

    let result = (await database('/balance/outcomes').orderByChild('employeeId').equalTo(employeeId ).once('value')).val() || {}


    return result
}

But it returns {}

Answer 1

You're trying to search too deep into your database, and you have a typo in your orderByChild method.

Because your structure is broken down by date and reference key - you need to search through the timestamps then the children.

{ 
  2018-02-27: {
    -L6MTxsb_aJoKhMNA6X0 : {
      comment: ...
      created: ...
      price : ...
    },
    -L6MTxsb_aJoKhCNA6X0 : {
      comment: ...
      created: ...
      price : ...
      employeeId: ...
    },
  },
  2018-02-27: {
    -L6MTxsb_aJoKhMNA6X0 : {
      comment: ...
      created: ...
      price : ...
    },
    -L6MTxsb_aJoKhCNA6X0 : {
      comment: ...
      created: ...
      price : ...
      employeeId: ...
    },
  },
};

You can pass the timestamp to the function as below;

export const loadForEmployee = async (employeeId, timestamp) => {
  const snapshots = await database('/balance/outcomes/' + timestamp)
    .orderByChild('employeeId')
    .equalTo(employeeId)
    .once('value');

  return snapshots.val() || {};
}

The other option is to iterate through all the results, but this will be fairly slow and intensive depending on how big your database is;

export const loadForEmployee = async employeeId => {
  const snapshots = await database('/balance/outcomes')
    .once('value');

  const results = {};

  snapshots.forEach(snapshot => {
    const timestamp = snapshot.key;

    const outcomes = snapshot.val();

    Object.keys(outcomes).forEach(key => {
      const outcome = outcomes[key];

      if (outcome.employeeId === employeeId) {
        if (!results[timestamp]) {
          results[timestamp] = {};
        }

        results[timestamp][key] = outcome;
      }
    });
  });

  return results;
}

I haven't tested this code, so it might not work verbatim but the general idea should be correct.