Salesforce does not limit the maximum number of rows that can be queried when using the Salesforce SOAP and REST APIs to retrieve record data, as in these contexts, the resources consuming and processing the resulting record data are off-platform.

One consideration to keep in mind, however, is the daily API limits—although you can read unlimited data, it is still chunked from the Salesforce servers and retrieving each chunk will consume an API call. Although less friendly, the Salesforce Bulk API is more efficient in retrieving more records while using fewer API calls to the Salesforce servers.