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This MongoDB article will explain how to query for non-null values ​​in MongoDB. To query for non-null values, you can use $nethe operator and $eqthe operator and then specify the desired value to query.

This article shows the readers how to query for non-null values ​​in MongoDB using various methods and examples. So, let’s get started with this guide.

$neOperators in MongoDB

The syntax of this operator is:

{ field: { $ne: value } }

$neThe operator selects all documents fieldwhose value of is different from the given . It includes documents that do not contain .valuefield

$eqOperators in MongoDB

This operator specifies an equality condition. For example, $eqthe operator matches documents where fieldthe value of is equal to the specified value.

The syntax for this operator is:

{ <field>: { $eq: <value> } }

Specifying $eqthe operator is equivalent to using the form { field: <value> }, except <value>that is a regular expression.

is Not NullQuerying values ​​in MongoDB

Now let’s help you get started by looking at an example of how to achieve this.

Below is the collection you will use to illustrate some operations.

db={
  "teams": [
    {
      team: "Manchester City",
      position: "1st",
      points: 70
    },
    {
      team: "Liverpool",
      position: null,
      points: 69
    },
    {
      team: "Chelsea",
      position: "3rd",
      points: 59
    },
    {
      team: "Arsenal",
      position: "4th",
      points: null
    },
    {
      team: "Tottenham",
      position: "5th",
      points: 51
    },
    {
      team: "Manchester United",
      position: "6th",
      points: 50
    },
  ]
}

$neOperator to query is Not Nullthe value of a string field in MongoDB

You will use $nethe operator to pass an expression to $nethe operator, which negates null values ​​for a specific field, to query for string fields that are not null in this example. For this example, you can use the following query.

db.teams.find({
  points: {
    $ne: null
  }
})

You find all pointssuch documents that have no field value specified as null.

$neQuerying on numeric fields with operators in MongoDBis Not Null

In this case, you will select those documents that do not have a numeric field with an empty value. For this example, you can use the following query.

db.teams.find({
  position: {
    $ne: null
  }
})

You can again find documents that do not have null as a value in the position field.

$neOperator to query non-null values ​​in MongoDB

In this example, you will use $nethe operator with a blank string to query MongoDB for non-null values.

Since the collection you used above does not have any such documents with blank string values, you can add some to the collection. The following documents will be added to the collection as shown below.

db={
  "teams": [
    {
      team: "Manchester City",
      position: "1st",
      points: 70
    },
    {
      team: "Liverpool",
      position: null,
      points: 69
    },
    {
      team: "Chelsea",
      position: "3rd",
      points: 59
    },
    {
      team: "Arsenal",
      position: "4th",
      points: null
    },
    {
      team: "Tottenham",
      position: "5th",
      points: 51
    },
    {
      team: "Manchester United",
      position: "6th",
      points: 50
    }, {
      team: "West Ham",
      position: "",
      points: 48
    },
    {
      team: "Wolves",
      position: "",
      points: 46
    }

  ]
}

OK, now you have two more documents added to your collection and you are good to go. You can now use $nethe operator to query for non-null values ​​by specifying a blank string.

For this example, you can use the following query.

db.teams.find({
  position: {
    $ne: ""
  }
})

This time you cannot find the newly added documents.

In MongoDB, $eqthe operator specifies a non-null value.

In this example, you will use $eqthe operator to query for non-null values ​​because you will pass a value to look for to query for that value in layman's terms 不是空.

Let's find the team ranked third. For this example, you can use the following query.

db.teams.find({
  position: {
    $eq: "3rd"
  }
})

You found the team currently ranked third in the collection.

So, with the help of this MongoDB article, you have learned how to query for non-null values ​​using the $neand $eqoperators.