# Querying data sources

### Reading from a CSV Data Source

You can read data from a CSV data source in a number of ways.

For illustration we will use this data source called "pets":

| id   | category | name    | status    |
| ---- | -------- | ------- | --------- |
| 1000 | birds    | Archie  | available |
| 1001 | dogs     | Zipper  | available |
| 1002 | dogs     | Teddy   | sold      |
| \*   | no data  | no data | no data   |

### Single value lookup with {{csv}}

The most basic query function is to return the value of one field (selected-column) given a field name to search (column-name) and a value to search for in that field (query-value). Of course the query-value would normally be pulled from the request.

Syntax:

```handlebars
{{csv 'data-source-name' 'column-name' 'query-value' 'selected-column' }}
```

Template Example: Display the Name of the pet with Id 1001

```handlebars
{{ csv 'pets' 'id' '1001' 'name' }}
```

Output:

```
Zipper
```

### More advanced examples: Single value lookup with {{csv}}

Template Example: Display the Name of the pet with Id taken from position 2 on the path

```handlebars
{{csv 'pets' 'id' 'Request.Path.[2]' 'name'}}
```

Template Example: Use conditional logic to check if a pet with Id taken from position 2 on the path exists, and if not return an error. Note that when the csv function is used within an #equal block, it needs to be enclosed in round brackets.

```handlebars
{{#equal (csv 'pets' 'id' 'Request.Path.[2]' 'name') 'no data'}}
    {{setStatusCode 404}}
{{else}}
.
.
{{/equal}}
```

###

### Retrieve all rows as a map with {{csvAsMap}}

Additional functions are available to query the CSV data source to return all or a filtered subset of it’s rows, as a map.

Retrieving the results as a map makes it simple to render back into the template, as you can use the {{this}} expression with the column names to identify which fields you want to render.

Note that as you will use this wrapped within an #each or #first block, the csvAsMap function must be enclosed inside round brackets.

See examples below.

Syntax:

```handlebars
{{csvAsMap 'data-source-name' }}
```

Template Example:

```handlebars
{
    "All-The-Pets": [ 
    {{#each (csvAsMap 'pets')}}
    {
        "id":{{this.id}}, 
        "category":"{{this.category}}", 
        "name":"{{this.name}}", 
        "status":"{{this.status}}"
    }
    {{#unless @last}},{{/unless}} 
    {{/each}} 
    ]
}
```

Output:

```json
{
    "All-The-Pets": [
        {
            "id": 1000,
            "category": "cats",
            "name": "Sylvester",
            "status": "available"
        },
        {
            "id": 1001,
            "category": "dogs",
            "name": "Zipper",
            "status": "available"
        },
        {
            "id": 1002,
            "category": "dogs",
            "name": "Teddy",
            "status": "sold"
        }
    ]
}
```

### Retrieve filtered rows as a map with {{csvMatchingRows}}

To filter the map on a single column value at the time of query you can use csvMatchingRows. This will return all the rows where the (column-name) = (query-value).

Note that as you will use this wrapped within an #each or #first block, the csvMatchingRows function must be enclosed inside round brackets.

```handlebars
{{csvMatchingRows 'data-source-name' 'column-name' 'query-value'}}
```

Template Example:

```handlebars
{
    "Dogs-Only": [ 
        {{#each (csvMatchingRows 'pets' 'category' 'dogs')}}
        {
            "id":{{this.id}}, 
            "category":"{{this.category}}", 
            "name":"{{this.name}}", 
            "status":"{{this.status}}"
        }
        {{#unless @last}},{{/unless}} {{/each}} 
        ]
}
```

Output:

```json
{
    "Dogs-Only": [
        {
            "id": 1001,
            "category": "dogs",
            "name": "Zipper",
            "status": "available"
        },
        {
            "id": 1002,
            "category": "dogs",
            "name": "Teddy",
            "status": "sold"
        }
    ]
}
```

### Advanced querying with SQL SELECT {{csvSqlCommand}}

A simplified SQL like syntax can be used to query the data in a csv data source and retrieve a map of the results. (This syntax can also be used to [UPDATE ](/create-simulations/using-data-sources-in-simulations/updating-data-in-data-sources.md)and [DELETE ](/create-simulations/using-data-sources-in-simulations/deleting-data-from-data-sources.md)from the data source. You cannot insert using this syntax however there is a mechanism which can be read about [here](/create-simulations/using-data-sources-in-simulations/inserting-data-into-a-data-source.md).)

Note that as you will use this wrapped within an #each or #first block, the csvSQLCommand must be enclosed inside round brackets.

You can read more about using this SQL like syntax [here](/create-simulations/using-data-sources-in-simulations/guidance-on-using-the-sql-like-syntax.md).

Syntax:

```handlebars
{{csvSqlCommand 'sql select, update or delete statement'}}
```

Template Example:

```handlebars
{
    "Dogs-With-Big-Ids-Only": [
    {{#each (csvSqlCommand "SELECT * FROM pets WHERE category = 'dogs' AND id >= '1002'")}}
        {
            "id":{{this.id}}, 
            "category":"{{this.category}}", 
            "name":"{{this.name}}", 
            "status":"{{this.status}}"
        }{{#unless @last}},{{/unless}}
    {{/each}}
    ]
}
```

Output:

```json
{
    "Dogs-With-Big-Ids-Only": [
        {
            "id": 1002,
            "category": "dogs",
            "name": "Violet",
            "status": "sold"
        }
    ]
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.cloud.hoverfly.io/create-simulations/using-data-sources-in-simulations/querying-data-sources.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.