Run SOQL parent-to-child and child-to-parent relationship queries via the Salesforce REST Query API

In-depth guide

Steps

1. For child-to-parent (many-to-one) traversal, use dot notation in the SELECT clause: SELECT Id, Account.Name FROM Contact WHERE Account.Industry = 'Technology'.
2. For parent-to-child (one-to-many) sub-queries, embed a SELECT inside the FROM clause: SELECT Id, Name, (SELECT Id, CloseDate FROM Opportunities) FROM Account.
3. GET or POST to /services/data/vXX.0/query?q={URL-encoded SOQL}; use POST /services/data/vXX.0/query for long queries that exceed URL length limits.
4. The response includes 'totalSize', 'done', and 'records'; if 'done' is false, follow 'nextRecordsUrl' to paginate until done is true.
5. For sub-query results, each parent record's sub-query results are nested under the relationship name with their own 'records' array and 'done'/'nextRecordsUrl' if the child result set is large.
6. Use LIMIT and OFFSET or cursor-based pagination (nextRecordsUrl) rather than OFFSET alone for large datasets, as OFFSET beyond 2,000 is not supported.