File: find.md

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To populate the database, please run the examples from the [previous section of the tutorial](inserting-into-the-database.md) 
as we will be using the same setup here.

## Finding documents

The basic syntax for finding multiple documents in the database is to call the class method `find()` 
or it's synonym `find_many()` with some search criteria (see next section): 

```python
findresult = Product.find(search_criteria)
```

This returns a `FindMany` object, which can be used to access the results in different ways. 
To loop through the results, use a `async for` loop:

```python
async for result in Product.find(search_criteria):
    print(result)
```

If you prefer a list of the results, then you can call `to_list()` method:

```python
result = await Product.find(search_criteria).to_list()
```

To get the first document, you can use `.first_or_none()` method. 
It returns the first found document or `None`, if no documents were found.

```python
result = await Product.find(search_criteria).first_or_none()
```

### Search criteria

As search criteria, Beanie supports Python-based syntax.
For comparisons Python comparison operators can be used on the class fields (and nested
fields):

```python
products = await Product.find(Product.price < 10).to_list()
```

This is supported for the following operators: `==`, `>`, `>=`, `<`, `<=`, `!=`.
Other MongoDB query operators can be used with the included wrappers. 
For example, the `$in` operator can be used as follows:

```python
from beanie.operators import In

products = await Product.find(
    In(Product.category.name, ["Chocolate", "Fruits"])
).to_list()
```

The whole list of the find query operators can be found [here](../api-documentation/operators/find.md).

For more complex cases native PyMongo syntax is also supported:

```python
products = await Product.find({"price": 1000}).to_list()
```

## Finding single documents

Sometimes you will only need to find a single document. 
If you are searching by `id`, then you can use the [get](../api-documentation/document.md/#documentget) method:

```python
bar = await Product.get("608da169eb9e17281f0ab2ff")
```

To find a single document via a single search criterion,
you can use the [find_one](../api-documentation/interfaces.md/#findinterfacefind_one) method:

```python
bar = await Product.find_one(Product.name == "Peanut Bar")
```

## Syncing from the Database

If you wish to apply changes from the database to the document, utilize the [sync](../api-documentation/document.md/#documentsync) method:

```python
await bar.sync()
```

Two merging strategies are available: `local` and `remote`.

### Remote Merge Strategy

The remote merge strategy replaces the local document with the one from the database, disregarding local changes:

```python
from beanie import MergeStrategy

await bar.sync(merge_strategy=MergeStrategy.remote)
```
The remote merge strategy is the default.

### Local Merge Strategy

The local merge strategy retains changes made locally to the document and updates other fields from the database.
**BE CAREFUL**: it may raise an `ApplyChangesException` in case of a merging conflict.

```python
from beanie import MergeStrategy

await bar.sync(merge_strategy=MergeStrategy.local)
```

## More complex queries

### Multiple search criteria

If you have multiple criteria to search against, 
you can pass them as separate arguments to any of the `find` functions:

```python
chocolates = await Product.find(
    Product.category.name == "Chocolate",
    Product.price < 5
).to_list()
```


Alternatively, you can chain `find` methods:

```python
chocolates = await Product
              .find(Product.category.name == "Chocolate")
              .find(Product.price < 5).to_list()
```

### Sorting

Sorting can be done with the [sort](../api-documentation/query.md/#findmanysort) method.

You can pass it one or multiple fields to sort by. You may optionally specify a `+` or `-` 
(denoting ascending and descending respectively).

```python
chocolates = await Product.find(
    Product.category.name == "Chocolate").sort(-Product.price,+Product.name).to_list()
```

You can also specify fields as strings or as tuples:

```python
chocolates = await Product.find(
    Product.category.name == "Chocolate").sort("-price","+name").to_list()

chocolates = await Product.find(
    Product.category.name == "Chocolate").sort(
    [
        (Product.price, pymongo.DESCENDING),
        (Product.name, pymongo.ASCENDING),
    ]
).to_list()
```

### Skip and limit

To skip a certain number of documents, or limit the total number of elements returned, 
the `skip` and `limit` methods can be used:
```python
chocolates = await Product.find(
    Product.category.name == "Chocolate").skip(2).to_list()

chocolates = await Product.find(
    Product.category.name == "Chocolate").limit(2).to_list()
```

### Projections

When only a part of a document is required, projections can save a lot of database bandwidth and processing.
For simple projections we can just define a pydantic model with the required fields and pass it to `project()` method:

```python
class ProductShortView(BaseModel):
    name: str
    price: float


chocolates = await Product.find(
    Product.category.name == "Chocolate").project(ProductShortView).to_list()
```

For more complex projections an inner `Settings` class with a `projection` field can be added:

```python
class ProductView(BaseModel):
    name: str
    category: str

    class Settings:
        projection = {"name": 1, "category": "$category.name"}


chocolates = await Product.find(
    Product.category.name == "Chocolate").project(ProductView).to_list()
```

### Finding all documents

If you ever want to find all documents, you can use the `find_all()` class method. This is equivalent to `find({})`.