# Computed fields

{% hint style="info" %}
This feature is in Alpha.
{% endhint %}

## Definition

A computed field is a dynamic field defined in the schema, linked to a script that is triggered for each new user activity or profile update and performs a computation of a function's result **on a regular basis**. It is used when the desired outcome cannot be achieved with existing directives or to simplify an OTQL query by replacing multiple directives with a single field.

Those fields can be used in segment definition to improve analysis and sharing, or in the ***Experiment*** feature to enhance control groups creation.

### Examples

Those examples are handled by computed fields:

* Retrieve the most recent event (e.g. last visit, last transaction, etc.)
* Get the total amount for a specific type of event (e.g. sum of transactions in the last 30 days, total expenditure on a particular category of product, etc.).
* Weighted sum (Affinity total, etc.)
* Compare multiple channels (e.g. to find the best channel for transactions).

This example should be handled by a standard directive:

* Get all users with at least a specific amount for one category

This example can't be handled by a computed field:

* Identify the top X% of a specific user group (e.g. the top 10% of buyers).

### **Usage Example**

Once live, a computed field behaves like a regular field, making it transparent to the user. Here's how you can use it in practice:

> Use Case: Identify Users Who Have Spent More Than 100€ on IT Products in the Last 3 Months

**With Standard Directives:**

```sql
// With standard directives
SELECT { id } FROM UserPoint
WHERE activity_events @ScoreSum(min : 100) {
    basket { 
        items @ScoreField(name:"price") @ScoreSum(result:"score_value") {
            category="IT" AND date >= "now-3M/M"
        }
    }
}
```

This query uses standard directives to sum the basket amounts for **IT** products over the last 3 months.

**With a Computed Field:**

```sql
//With a COmputed field "IT_amount_3months"
SELECT { id } FROM UserPoint WHERE IT_amount_3months >= 100
```

In this version, the computed field `IT_amount_3months` is used directly in the query. The field is calculated on a regular basis, meaning no computation is performed during query execution. This results gives faster query response times, as the value is precomputed and readily available.


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