MongoDB - Query Operators

In MongoDB, query operators are used to specify conditions in queries. They allow you to filter documents based on various criteria. Here are some common MongoDB query operators:

Comparison Operators:

1. Equality:

   • $eq: Matches values that are equal to a specified value.

     db.collection_name.find({ field: { $eq: value } });

2. Inequality:

   • $ne: Matches values that are not equal to a specified value.

     db.collection_name.find({ field: { $ne: value } });

3. Greater Than:

   • $gt: Matches values that are greater than a specified value.

     db.collection_name.find({ field: { $gt: value } });

4. Greater Than or Equal To:

   • $gte: Matches values that are greater than or equal to a specified value.

     db.collection_name.find({ field: { $gte: value } });

5. Less Than:

   • $lt: Matches values that are less than a specified value.

     db.collection_name.find({ field: { $lt: value } });

6. Less Than or Equal To:

   • $lte: Matches values that are less than or equal to a specified value.

     db.collection_name.find({ field: { $lte: value } });

Logical Operators:

1. Logical AND:

   • $and: Joins query clauses with a logical AND.

     db.collection_name.find({ $and: [ { field1: value1 }, { field2: value2 } ] });

2. Logical OR:

   • $or: Joins query clauses with a logical OR.

     db.collection_name.find({ $or: [ { field1: value1 }, { field2: value2 } ] });

3. Logical NOT:

   • $not: Inverts the effect of a query expression and returns documents that do not match the query expression.

     db.collection_name.find({ field: { $not: { $eq: value } } });

Element Operators:

1. Existence:

   • $exists: Matches documents that have the specified field.

     db.collection_name.find({ field: { $exists: true } });

2. Type:

   • $type: Matches documents where the value of a field is of the specified BSON data type.

     db.collection_name.find({ field: { $type: "string" } });

Array Operators:

1. Element in Array:

   • $in: Matches any of the values specified in an array.

     db.collection_name.find({ field: { $in: [value1, value2] } });

2. All Elements in Array:

   • $all: Matches arrays that contain all elements specified in the query.

     db.collection_name.find({ field: { $all: [value1, value2] } });

3. Size of Array:

   • $size: Matches arrays with a specific number of elements.

     db.collection_name.find({ field: { $size: 3 } });