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Select All Documents in a Collection

This operation uses a filter predicate of {}, which corresponds to the following SQL statement:

SELECT * FROM inventory

Specify Equality Condition

The following example selects from the inventory collection all documents where the status equals "D":

This operation uses a filter predicate of { status: "D" }, which corresponds to the following SQL statement:

SELECT * FROM inventory WHERE status = "D"

Specify Conditions Using Query Operators

The following example retrieves all documents from the inventory collection where status equals either "A" or "D":

Note

Although you can express this query using the $or operator, use the $in operator rather than the $or operator when performing equality checks on the same field.

The operation uses a filter predicate of { status: { $in: [ "A", "D" ] } }, which corresponds to the following SQL statement:

SELECT * FROM inventory WHERE status in ("A", "D")

Refer to the Query and Projection Operators document for the complete list of MongoDB query operators.

Specify AND Conditions

A compound query can specify conditions for more than one field in the collection's documents. Implicitly, a logical AND conjunction connects the clauses of a compound query so that the query selects the documents in the collection that match all the conditions.

The following example retrieves all documents in the inventory collection where the status equals "A" and qty is less than ($lt) 30:

The operation uses a filter predicate of { status: "A", qty: { $lt: 30 } }, which corresponds to the following SQL statement:

SELECT * FROM inventory WHERE status = "A" AND qty < 30

See comparison operators for other MongoDB comparison operators.

Specify OR Conditions

Using the $or operator, you can specify a compound query that joins each clause with a logical OR conjunction so that the query selects the documents in the collection that match at least one condition.

The following example retrieves all documents in the collection where the status equals "A" or qty is less than ($lt) 30:

The operation uses a filter predicate of { $or: [ { status: 'A' }, { qty: { $lt: 30 } } ] }, which corresponds to the following SQL statement:

SELECT * FROM inventory WHERE status = "A" OR qty < 30

Note

Queries that use comparison operators are subject to Type Bracketing.

Specify AND as well as OR Conditions

In the following example, the compound query document selects all documents in the collection where the status equals "A" and either qty is less than ($lt) 30 or item starts with the character p:

The operation uses a filter predicate of:

{
   status: 'A',
   $or: [
     { qty: { $lt: 30 } }, { item: { $regex: '^p' } }
   ]
}

which corresponds to the following SQL statement:

SELECT * FROM inventory WHERE status = "A" AND ( qty < 30 OR item LIKE "p%")

Note

MongoDB supports regular expressions $regex queries to perform string pattern matches.

Additional Query Tutorials

For additional query examples, see:

Behavior

Cursor

Read Isolation

For reads to Replica sets and replica set shards, read concern allows clients to choose a level of isolation for their reads. For more information, see Read Concern.

Query Result Format

When you run a find operation with a MongoDB driver or mongosh, the command returns a cursor that manages query results. The query results are not returned as an array of documents.

To learn how to iterate through documents in a cursor, refer to your driver's documentation. If you are using mongosh, see Iterate a Cursor in mongosh.