Efficient Steps to Diagnose and Fix Empty Data Query Issues

When developing applications, a common bug is that a data query returns empty results, causing the front‑end to display no data or the back‑end to return an empty list.

The article presents a classic four‑step troubleshooting workflow.

Step 1: Locate the Problem Boundary

First determine whether the issue originates from the front‑end or the back‑end by inspecting the network request in the browser’s developer console (F12). Open the Network tab, refresh or trigger the request, and examine the response preview. If the back‑end returns data, the problem lies in the front‑end code (e.g., wrong data path, missing rendering logic). If the back‑end returns no data, verify the request parameters.

Step 2: Backend Request Validation

On the server side, enable debug mode and examine the incoming request parameters line by line. Ensure the front‑end sends the expected parameters before diving into database or business‑logic analysis.

Step 3: Backend Database Query Validation

After reaching the database query stage, focus on two points: (1) whether the query wrapper (e.g., MyBatis‑Plus QueryWrapper) contains correct conditions, and (2) whether the query result set actually contains records. For MyBatis‑Plus, check if records.size() > 0. To see the exact SQL, enable SQL logging in application.yml:

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

Run the query, copy the printed SQL, and execute it directly in the database console to verify that data is returned. If the SQL returns no rows, the issue is with the query conditions or missing data.

Step 4: Backend Data‑Processing Logic Validation

If the database returns data but the response sent to the front‑end is still empty, continue debugging after the query to check for filtering, permission masking, or incorrect field mapping that may discard the results.

Conclusion

By following these four steps—collecting information, locating the problem boundary, validating requests and queries, and inspecting data‑handling logic—you can efficiently resolve empty‑data bugs in both front‑end and back‑end code.