# Using Variables in your Custom Query

### Overview

Neurelo custom queries support variables so that values can be passed in to your queries during run time execution. Here is how to add a variable"

```sql
SELECT * FROM "User" where id = {{ id }}
```

In the above query, {{ id }} is a variable that requires the user to pass the value of "id" at the when calling the endpoint for run-time execution.

{% hint style="info" %}
When you add a variable to a custom query, remember to specify the data-type for the variable
{% endhint %}

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### Accessing custom query API endpoints with variables

Once you have a custom query with variables saved and deployed, you can use them depending on the `HTTP Method` defined in the custom query

* GET & DELETE methods will use the query string params to pass the values for the variables in the request URL. e.g.

  `${API_URL}/custom/query?id=1`
* POST, PATCH & PUT methods will use values for the variables specified in the request body, assuming the body is a valid JSON:

```sql
{
  "id": 1,
  "anotherParameter": "Here"
}
```

### Important considerations

* Variables do not need to be wrapped between single or double quotes for string datatypes, as we do the right parsing in our back end.

```sql
## Wrong
SELECT * FROM "Users" where id = '{{ id }}'

## Correct
SELECT * FROM "Users" where id = {{ id }}
```

* SQL Queries run as [Parametrized Queries](https://cheatsheetseries.owasp.org/cheatsheets/Query_Parameterization_Cheat_Sheet.html), meaning queries are protected from SQL Injection.
* Supported variable types are:
  * Int
  * String
  * Array
  * Boolean
  * Float
* A `List` variables purpose is to provide a list of values to be **spread** as the different elements of an array to be used in an `IN` clause in SQL, so that your queries can look like this:

```sql
SELECT * FROM users WHERE id IN {{ ids }}

## Can turn into
SELECT * FROM users where id IN ($id1, $id2, ...)
```