> ## Documentation Index
> Fetch the complete documentation index at: https://docs.blnkfinance.com/llms.txt
> Use this file to discover all available pages before exploring further.

# JOINs

> Learn how to retrieve related data across collections in a single search query

export const CtaCallout = props => {
  const {title, buttonLabel, href, trackingEvent, buttonTarget, rel = "noopener noreferrer", children} = props;
  const handleCtaClick = () => {
    if (typeof window === "undefined" || !trackingEvent) {
      return;
    }
    try {
      window.dispatchEvent(new CustomEvent("blnk:docs-cta", {
        detail: {
          name: trackingEvent,
          href
        }
      }));
    } catch {}
    try {
      window.posthog?.capture?.(trackingEvent, {
        href
      });
    } catch {}
    const gaPayload = {
      cta_href: href
    };
    try {
      window.gtag?.("event", trackingEvent, gaPayload);
    } catch {}
    try {
      window.dataLayer = window.dataLayer || [];
      window.dataLayer.push({
        event: trackingEvent,
        ...gaPayload
      });
    } catch {}
  };
  const isExternal = typeof href === "string" && (/^https?:\/\//i).test(href);
  const target = buttonTarget ?? (isExternal ? "_blank" : undefined);
  const linkRel = isExternal ? rel : undefined;
  return <section className="cta-callout not-prose relative my-8 w-full min-w-0 overflow-hidden rounded-xl border border-zinc-200 p-5 dark:border-white/10">
      <div className="cta-callout-noise" aria-hidden="true" />
      <div className="cta-callout-layout">
        {title ? <div className="cta-callout-title-row">
            <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 28 28" width="14" height="14" className="cta-callout-icon shrink-0 text-zinc-800 dark:text-zinc-200" aria-hidden="true">
              <g fill="none" fillRule="nonzero">
                <path d="M28 0v28H0V0h28ZM14.691833333333335 27.134333333333334l-0.012833333333333334 0.0023333333333333335 -0.08283333333333333 0.04083333333333334 -0.023333333333333334 0.004666666666666667 -0.016333333333333335 -0.004666666666666667 -0.08283333333333333 -0.04083333333333334c-0.011666666666666667 -0.004666666666666667 -0.022166666666666668 -0.0011666666666666668 -0.028000000000000004 0.005833333333333334l-0.004666666666666667 0.011666666666666667 -0.019833333333333335 0.49933333333333335 0.005833333333333334 0.023333333333333334 0.011666666666666667 0.015166666666666667 0.12133333333333333 0.08633333333333333 0.0175 0.004666666666666667 0.014000000000000002 -0.004666666666666667 0.12133333333333333 -0.08633333333333333 0.014000000000000002 -0.018666666666666668 0.004666666666666667 -0.019833333333333335 -0.019833333333333335 -0.4981666666666667c-0.0023333333333333335 -0.011666666666666667 -0.0105 -0.019833333333333335 -0.019833333333333335 -0.021Zm0.3091666666666667 -0.13183333333333336 -0.015166666666666667 0.0023333333333333335 -0.21583333333333335 0.1085 -0.011666666666666667 0.011666666666666667 -0.0035000000000000005 0.012833333333333334 0.021 0.5016666666666667 0.005833333333333334 0.014000000000000002 0.009333333333333334 0.008166666666666668 0.23450000000000004 0.1085c0.014000000000000002 0.004666666666666667 0.026833333333333334 0 0.03383333333333334 -0.009333333333333334l0.004666666666666667 -0.016333333333333335 -0.03966666666666667 -0.7163333333333334c-0.0035000000000000005 -0.014000000000000002 -0.011666666666666667 -0.023333333333333334 -0.023333333333333334 -0.025666666666666667Zm-0.8341666666666667 0.0023333333333333335a0.026833333333333334 0.026833333333334334 0 0 0 -0.0315 0.007000000000000001l-0.007000000000000001 0.016333333333333335 -0.03966666666666667 0.7163333333333334c0 0.014000000000000002 0.008166666666666668 0.023333333333333334 0.019833333333333335 0.028000000000000004l0.0175 -0.0023333333333333335 0.23450000000000004 -0.1085 0.011666666666666667 -0.009333333333333334 0.004666666666666667 -0.012833333333333334 0.019833333333333335 -0.5016666666666667 -0.0035000000000000005 -0.014000000000000002 -0.011666666666666667 -0.011666666666666667 -0.21466666666666667 -0.10733333333333334Z" strokeWidth="1.1667" />
                <path fill="currentColor" d="M14 2.916666666666667A1.75 1.75 0 0 1 15.750000000000002 4.666666666666667v6.302333333333334L21.207666666666668 7.816666666666667a1.75 1.75 0 0 1 1.75 3.031L17.5 14l5.457666666666667 3.151166666666667a1.75 1.75 0 0 1 -1.75 3.031l-5.457666666666667 -3.1500000000000004V23.333333333333336a1.75 1.75 0 0 1 -3.5 0v-6.302333333333334L6.792333333333334 20.183333333333337a1.75 1.75 0 1 1 -1.75 -3.031L10.5 14 5.042333333333334 10.848833333333333a1.75 1.75 0 0 1 1.75 -3.031l5.457666666666667 3.1500000000000004V4.666666666666667A1.75 1.75 0 0 1 14 2.916666666666667Z" strokeWidth="1.1667" />
              </g>
            </svg>
            <p className="cta-callout-title min-w-0 font-semibold text-zinc-800 dark:text-zinc-200">
              {title}
            </p>
          </div> : null}
        <div className={`cta-callout-body text-sm leading-normal text-zinc-800 dark:text-zinc-200${title ? " cta-callout-body--indented" : ""}`}>
          {children}
        </div>
        <a href={href} target={target} rel={linkRel} onClick={handleCtaClick} data-docs-cta={trackingEvent || undefined} className="cta-callout-button inline-flex items-center justify-center gap-1 rounded-full bg-white px-3 py-1.5 text-sm font-semibold transition hover:bg-zinc-100 focus-visible:outline focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-white/50 dark:bg-white dark:hover:bg-zinc-200">
          {buttonLabel}
          <span className="cta-callout-button-arrow" aria-hidden="true">
            →
          </span>
        </a>
      </div>
    </section>;
};

<Info>Available in version 0.11.3 and later.</Info>

JOINs let you pull related data from other collections into the collection you are querying.

Let's say you want to fetch a list of balances, but also want to see the identity info linked to the balances; with JOIN, you can do that in one request.

Blnk links collections through `_id` fields. For example, a balance uses `identity_id` to point to the matching `identity_id` in the identities collection.

***

## Retrieving related data

Use `include_fields` to tell the Search API which related collection to return as part of your results. The format is:

* `$collection_name(*)` to include all fields
* `$collection_name(field1,field2,field3)` to include specific fields.

For example, when you search for balances, you can fetch the identity linked to each balance:

<CodeGroup>
  ```json Show all fields theme={"system"}
  {
    "q": "*",
    "include_fields": "$identities(*)"
  }'
  ```

  ```json Show specific fields theme={"system"}
  {
    "q": "*",
    "include_fields": "$identities(first_name,last_name,email)"
  }'
  ```
</CodeGroup>

The response will include an `identities` object populated with the identity details of the balance.

```json Response (all fields) {15-36} expandable theme={"system"}
{
  "facet_counts": [],
  "found": 144,
  "hits": [
  {
    "document": {
        "balance": "9848100",
        "balance_id": "bln_d9eb274a-d8bb-4ada-bc62-541d5e0073ac",
        "created_at": 1763661598,
        "credit_balance": "9848100",
        "currency": "GBP",
        "debit_balance": "0",
        "id": "bln_d9eb274a-d8bb-4ada-bc62-541d5e0073ac",
        "identities": {
          "category": "",
          "city": "",
          "country": "Mexico",
          "created_at": 1763661592,
          "dob": 1763661592,
          "email_address": "graciela.rosas@example.com",
          "first_name": "Graciela",
          "gender": "",
          "id": "idt_8cc22560-5ace-4989-8953-fcbad7947d48",
          "identity_id": "idt_8cc22560-5ace-4989-8953-fcbad7947d48",
          "identity_type": "",
          "last_name": "Rosas",
          "meta_data": {},
          "nationality": "",
          "organization_name": "",
          "other_names": "",
          "phone_number": "",
          "post_code": "",
          "state": "Guanajuato",
          "street": "3936 Prolongación Norte Coronado"
        },
        "identity_id": "idt_8cc22560-5ace-4989-8953-fcbad7947d48",
        "indicator": "",
        "inflight_balance": "0",
        "inflight_credit_balance": "0",
        "inflight_debit_balance": "0",
        "inflight_expires_at": 1763661598,
        "ledger_id": "ldg_ad728e47-b730-4356-b1a7-703f42d33f87",
        "meta_data": { },
        "version": 2
      },
      "highlight": {},
      "highlights": []
    }
  ]
}
```

```json Response (specific fields) {15-19} expandable theme={"system"}
{
  "facet_counts": [],
  "found": 144,
  "hits": [
  {
    "document": {
        "balance": "9848100",
        "balance_id": "bln_d9eb274a-d8bb-4ada-bc62-541d5e0073ac",
        "created_at": 1763661598,
        "credit_balance": "9848100",
        "currency": "GBP",
        "debit_balance": "0",
        "id": "bln_d9eb274a-d8bb-4ada-bc62-541d5e0073ac",
        "identities": {
          "email_address": "graciela.rosas@example.com",
          "first_name": "Graciela",
          "last_name": "Rosas"
        },
        "identity_id": "idt_8cc22560-5ace-4989-8953-fcbad7947d48",
        "indicator": "",
        "inflight_balance": "0",
        "inflight_credit_balance": "0",
        "inflight_debit_balance": "0",
        "inflight_expires_at": 1763661598,
        "ledger_id": "ldg_ad728e47-b730-4356-b1a7-703f42d33f87",
        "meta_data": { },
        "version": 2
      },
      "highlight": {},
      "highlights": []
    }
  ]
}
```

<Note>
  Balance search documents do not include `precision`. Use the precision you apply to transactions for each currency when converting balance integers to display amounts.
</Note>

<Tip>
  You can include multiple related collections in your results, e.g., `$ledgers(*), $identities(first_name,last_name,email)`.
</Tip>

***

## Filter by related data

You can filter a collection using related data from another collection. For example, let's say you want to only view identities that have a USD balance:

* First, you'll search for all identities – `/search/identities`.
* Then add a "balance" filter to only include identities linked to a USD balance.
* Finally, you can specify what balance fields you want to include in the results.

<CodeGroup>
  ```json Request theme={"system"}
  {
    "q": "*",
    "filter_by": "$balances(currency:=USD)",
    "include_fields": "$balances(balance_id,currency,balance,credit_balance,debit_balance)"
  }
  ```
</CodeGroup>

```json Response {7-13, 40-46} expandable theme={"system"}
{
  "facet_counts": [],
  "found": 48,
  "hits": [
    {
      "document": {
        "balances": {
          "balance": "16712100",
          "balance_id": "bln_f933c83c-dc40-4a48-b063-45039173c218",
          "credit_balance": "61033900",
          "currency": "USD",
          "debit_balance": "44321800"
        },
        "category": "",
        "city": "",
        "country": "United Kingdom",
        "created_at": 1763661596,
        "dob": 1763661596,
        "email_address": "debra.barrett@example.com",
        "first_name": "Debra",
        "gender": "",
        "id": "idt_651d448d-772d-4ae3-a878-836d39600e4a",
        "identity_id": "idt_651d448d-772d-4ae3-a878-836d39600e4a",
        "identity_type": "",
        "last_name": "Barrett",
        "meta_data": {},
        "nationality": "",
        "organization_name": "",
        "other_names": "",
        "phone_number": "",
        "post_code": "",
        "state": "West Midlands",
        "street": "7028 Victoria Road"
      },
      "highlight": {},
      "highlights": []
    },
    {
      "document": {
        "balances": {
          "balance": "984000",
          "balance_id": "bln_c7d7c125-2d9b-438f-b99a-1ee7a7ff4000",
          "credit_balance": "44825600",
          "currency": "USD",
          "debit_balance": "43841600"
        },
        "category": "",
        "city": "",
        "country": "Ireland",
        "created_at": 1763661596,
        "dob": 1763661596,
        "email_address": "darrell.payne@example.com",
        "first_name": "Darrell",
        "gender": "",
        "id": "idt_8752147a-f97b-4d32-842e-92d360774fcf",
        "identity_id": "idt_8752147a-f97b-4d32-842e-92d360774fcf",
        "identity_type": "",
        "last_name": "Payne",
        "meta_data": {},
        "nationality": "",
        "organization_name": "",
        "other_names": "",
        "phone_number": "",
        "post_code": "",
        "state": "Mayo",
        "street": "2441 George Street"
      },
      "highlight": {},
      "highlights": []
    }
  ],
  "out_of": 48,
  "page": 1,
  "request_params": {
    "collection_name": "identities",
    "per_page": 2,
    "q": "*"
  },
  "search_cutoff": false,
  "search_time_ms": 14
}
```

<Note>
  The fields you include when filtering must be from the collection you are filtering by. In this example, we are filtering by balances, so we can only include fields from the balances collection.
</Note>

Another example: you want to view all balances that has sent money at least once to a particular balance:

* First, you'll search for all balances – `/search/balances`.
* Next, add a "transactions" filter so you only return balances that were involved in a transaction where the destination matches the target balance.
* Finally, you can specify what transaction fields you want to include in the results.

```json Request wrap theme={"system"}
{
  "q": "*",
  "filter_by": "$transactions(destination:=bln_1234567890)",
  "include_fields": "$transactions(transaction_id, amount, currency, status, created_at)"
}
```

***

## Merging / nesting joined fields

When the joined collection returns one result per document, the collection's fields are returned as nested objects. For example, see our first example response:

```json expandable theme={"system"}
{
  "facet_counts": [],
  "found": 144,
  "hits": [
    {
      "document": {
        "balance": "9848100",
        "balance_id": "bln_d9eb274a-d8bb-4ada-bc62-541d5e0073ac",
        "identities": {
          "email_address": "graciela.rosas@example.com",
          "first_name": "Graciela",
          "last_name": "Rosas"
        }
      }
    }
  ]
}
```

You can merge the joined fields to the main document by specifying `strategy:merge` in your request.

```json Request theme={"system"}
{
  "q": "*",
  "include_fields": "$identities(*, strategy:merge)"
}
```

```json Merged response theme={"system"}
{
  "facet_counts": [],
  "found": 144,
  "hits": [
  {
    "document": {
        "balance": "9848100",
        "balance_id": "bln_d9eb274a-d8bb-4ada-bc62-541d5e0073ac",
        "email_address": "graciela.rosas@example.com",
        "first_name": "Graciela",
        "last_name": "Rosas"
      }
    }
  ]
}
```

### Handling nested arrays

When a join returns more than one match, the Search API gives you an array. When there is only one match, it becomes an object. This can make the shape inconsistent.

To keep it consistent, add `strategy:nest_array` so the joined data is always returned as an array. Example:

```json Request theme={"system"}
{
  "q": "*",
  "include_fields": "$balances(*, strategy:nest_array)"
}
```

This ensures the joined `balances` data is always an array, no matter how many results it contains.

***

## Nested JOINs

You can stack JOINs to go deeper. For example, you can join a balance to its identity, then also join that same balance to its ledger in the same query.

<CodeGroup>
  ```json Request wrap theme={"system"}
  {
    "q": "*",
    "include_fields": "$balances(balance, currency, $ledgers(*), strategy:nest_array)"
  }
  ```
</CodeGroup>

```json Response  expandable theme={"system"}
{
  "facet_counts": [],
  "found": 48,
  "hits": [
    {
      "document": {
        "balances": [
          {
            "balance": "16712100",
            "currency": "USD",
            "ledgers": {
              "created_at": 1763661567,
              "ledger_id": "ldg_ad728e47-b730-4356-b1a7-703f42d33f87",
              "meta_data": {},
              "name": "Customers Ledger"
            }
          }
        ],
        "email_address": "debra.barrett@example.com",
        "first_name": "Debra",
        "identity_id": "idt_651d448d-772d-4ae3-a878-836d39600e4a",
        "last_name": "Barrett"
      }
    }
  ]
}
```

***

## Need help?

We are very happy to help you make the most of Blnk, regardless of whether it is your first time or you are switching from another tool.

To ask questions or discuss issues, please [contact us](mailto:support@blnkfinance.com) or [join our Discord community](https://discord.gg/7WNv94zPpx).

<CtaCallout title="Connect your ledger to Blnk Cloud" href="https://cloud.blnkfinance.com/auth/sign-up?utm_source=blnk_docs&utm_medium=documentation&utm_campaign=need-help" buttonLabel="Open Blnk Cloud" trackingEvent="clicked_cloud_signup">
  Sign up and manage your ledger with our back-office dashboard. You can invite teammates to collaborate and manage your ledger operations directly from the dashboard.
</CtaCallout>