# Clickhouse

Marple integrates seamlessly with [Clickhouse](https://clickhouse.com/), a fast analytical database. 

### Required credentials

To connect, the following credentials are needed:

```json
// example
{
    "dbHost": "play.clickhouse.com",
    "dbPort": "443",
    "dbName": "play",
    "dbUser": "user",
    "dbPassword": "secret"
}
```

### Queries

Queries are executed using SQL. Marple offers predefined queries for fetching datasets, signals, and time-series data. Below are some example queries:

* To retrieve **datasets**:

```sql
select
    concat("carId", ' ', session) as display_name,
    "carId",
    event,
    session,
    min(time) as start,
    max(time) as stop,
    realtime
  from {{TABLE}}
  group by "carId", event, session, realtime
```

* To retrieve a **signal list:**

```sql
select 
  name,
  sum(count) as count,
  max(count):: double precision *(1e9) as frequency
  unit,
  description
from {{TABLE}}
where "carId" = '{{ dataset.carId }}'
group by name
```

* To retrieve the **time series data**

```sql
select time / 1e9 as "timestamp", value
from {{TABLE}}
where "carId" = '{{ dataset.carId }}'
{%- if timestamp_start %}
and ({{timestamp_start}} * 1e9)::bigint <= time
{%- endif %}
{%- if timestamp_stop %}
and ({{timestamp_stop}} * 1e9)::bigint >= time
{%- endif %}
and name = '{{ signal.name }}'
```