When you query a remote system that runs a connector that is a different platform from the local system connector, data is converted to satisfy the target database requirements. Even when the initiator and target connectors are the same, the data is still transformed because the host formats might be different from each other.
It is important to note the following information about data types:
- The mapping for some data types may not preserve the data in all cases, so be aware that with some queries, data loss can occur.
As an example, the import of data from Presto with an unlimited VARCHAR size into a limited Teradata VARCHAR column requires truncation and thus, data loss.
As another example, if you export a Teradata byteint data type as a Boolean on Hive and then import it again, the data may not be the same. This can occur because the Boolean zero or one is imported while the byteint may have contained other values beyond zero or one.
- If a data type is unsupported on the remote system, and the metadata information retrieved contains a global type that is not supported on the initiator system, an error is returned from the initiator. For SELECT * queries with a column containing an unsupported data type, the unsupported column causes the entire query to return an error. In this case the query must include only the supported columns in the select list.
- All time-related data types are in UTC.