---
title: "minKey"
description: "Returns org.bson.types.MinKey, used in filters for the MongoDB Perspective binding expression."
---

# minKey

> Returns org.bson.types.MinKey, used in filters for the MongoDB Perspective binding expression.

**This function is used by Ignition's Expression language.**

## Description
## Syntax
`minKey()`

### Parameters
**None**

### Results
**MinKey** - A special data type that will match with document fields of the same MinKey type.

## Example
```py title="Code Snippet"
// In this example, we are querying for weather data documents using the field “elevation”
// In a Perspective MongoDB Binding, the expression below is applied to “value” of
// filter { _id: “value” }
 
minKey() // binding will return entire document(s) where minKey is found
```