Enriching Rows with External API Data

How to pull live data from external REST APIs into MySQL query results using VillageSQL’s vsql_http extension.

VillageSQL is a drop-in replacement for MySQL with extensions.

All examples in this guide work on VillageSQL. Install Now →

Some data doesn’t live in your database — exchange rates, shipping status, geolocation lookups, third-party product details. The standard approach is to fetch it in application code and either cache it in a table or stitch it together with query results at the application layer. VillageSQL’s vsql_http extension lets you pull that data directly from a query or store it in a column with a single UPDATE.

Setup

INSTALL EXTENSION vsql_http;

Pattern 1: Store Enrichment in a Column

The most common use: backfill a column with data fetched from an external API. Run an UPDATE that calls the API per row, store the result, then query the stored column.

This example fetches a shipping status for each order:

ALTER TABLE orders ADD COLUMN shipping_status VARCHAR(100);

UPDATE orders
SET shipping_status = JSON_VALUE(
  CONVERT(
    vsql_http.http_get(
      CONCAT('https://api.shipping.com/track/', tracking_number)
    ) USING utf8mb4
  ),
  '$.content.status'
)
WHERE tracking_number IS NOT NULL
  AND shipping_status IS NULL
LIMIT 50;

Run this in a loop from your application until no rows with shipping_status IS NULL remain. Process in batches to stay within API rate limits.

After backfilling, queries hit the stored column — no API call per query:

SELECT id, customer_id, shipping_status
FROM orders
WHERE shipping_status = 'delivered'
ORDER BY updated_at DESC;

Pattern 2: Live Lookup in a Query

For data that changes too fast to cache — exchange rates, real-time pricing — you can call the API inline in the SELECT. Every row in the result triggers a request, so keep the result set small.

-- Fetch the current USD/EUR exchange rate and apply it to each row
SET @rate_resp = CONVERT(
  vsql_http.http_get('https://api.exchangerate.example.com/latest?base=USD')
  USING utf8mb4
);
SET @eur_rate = CAST(JSON_VALUE(@rate_resp, '$.content.rates.EUR') AS DECIMAL(10,6));

SELECT
  id,
  amount_usd,
  ROUND(amount_usd * @eur_rate, 2) AS amount_eur
FROM invoices
WHERE currency = 'USD'
LIMIT 100;

Fetch the shared value once into a variable, then use the variable in the query — don’t call http_get() inside the SELECT expression unless each row genuinely needs a different API call.

Pattern 3: Conditional Enrichment

Only fetch for rows that actually need it using WHERE to filter before calling the API:

-- Only enrich rows missing geocoordinates
UPDATE locations
SET
  lat = CAST(JSON_VALUE(
    CONVERT(
      vsql_http.http_get(
        CONCAT('https://api.geocode.example.com/json?address=',
               vsql_http.url_encode(address))
      ) USING utf8mb4
    ),
    '$.content.lat'
  ) AS DECIMAL(10,7)),
  lng = CAST(JSON_VALUE(
    CONVERT(
      vsql_http.http_get(
        CONCAT('https://api.geocode.example.com/json?address=',
               vsql_http.url_encode(address))
      ) USING utf8mb4
    ),
    '$.content.lng'
  ) AS DECIMAL(10,7))
WHERE lat IS NULL
  AND address IS NOT NULL
LIMIT 25;

Note url_encode() wrapping the address — always encode user data before embedding it in a URL.

Handling API Errors

All vsql_http functions return NULL on connection failure. Check the status code before using the content:

SET @resp = CONVERT(
  vsql_http.http_get('https://api.example.com/data/123') USING utf8mb4
);

SELECT
  CASE
    WHEN @resp IS NULL          THEN 'connection_failed'
    WHEN JSON_VALUE(@resp, '$.status') = '200' THEN
      JSON_UNQUOTE(JSON_EXTRACT(@resp, '$.content'))
    WHEN JSON_VALUE(@resp, '$.status') = '404' THEN 'not_found'
    ELSE CONCAT('error_', JSON_VALUE(@resp, '$.status'))
  END AS result;

For bulk UPDATE loops, rows that get a NULL or non-200 response keep their column value NULL, so you can re-run the UPDATE to retry failed rows.

Performance Considerations

Each HTTP call is synchronous and blocks the query. A batch of 50 rows each hitting a 200ms API takes 10 seconds minimum. Set max_execution_time accordingly:

SET SESSION max_execution_time = 120000;  -- 2 minutes

UPDATE orders
SET shipping_status = JSON_VALUE(
  CONVERT(vsql_http.http_get(
    CONCAT('https://api.shipping.com/track/', tracking_number)
  ) USING utf8mb4),
  '$.content.status'
)
WHERE shipping_status IS NULL
LIMIT 50;

Prefer storing results over querying live — once a value is in a column, subsequent queries don’t touch the network.

Troubleshooting

Problem	Solution
UPDATE times out	Reduce LIMIT and set max_execution_time
Returns NULL for all rows	API unreachable from server host; verify network access
JSON extraction returns NULL	Response body large — use JSON_UNQUOTE(JSON_EXTRACT(...))
URL parameters not encoding correctly	Wrap values with vsql_http.url_encode()
Rate limit errors from API	Reduce LIMIT per batch; add SELECT SLEEP(1) between batches

Next Steps

• Making HTTP requests from SQL — full function reference and response parsing
• Sending webhooks from triggers — push changes out instead of pulling data in

See also

• Making HTTP Requests from SQL — the HTTP functions used for API calls
• JSON in MySQL — parsing the JSON responses returned by APIs