@zahra Jalilpour​ 

How the DLT tables and views are updated depends on the update type:

• Refresh all: All live tables are updated to reflect the current state of their input data sources. For all streaming tables, new rows are appended to the table.
• Full refresh all: All live tables are updated to reflect the current state of their input data sources. For all streaming tables, Delta Live Tables attempts to clear all data from each table and then load all data from the streaming source.

For existing live tables, an update has the same behavior as a SQL REFRESH on a materialized view. For new live tables, the behavior is the same as a SQL CREATE operation.