Query Documents
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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
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.