On Edit tab, you can view and write complex SQL statements that cannot be defined using the Design tab. When you switch from the Design tab to the Edit tab, the SQL in the Design tab is constructed and displayed as a complete SQL statement in the later
You can also write dynamic SQL Queries on Edit tab. Refer below section to know how to write dynamic SQL Query.
The SQL statement in the Edit tab will be used as the final SQL for compilation.
To prevent a complex query (defined in the Edit tab) from being overwritten, when you switch over to the Design tab, make some changes, and get back to Edit tab; you will be prompted with a dialog.
If you select Yes, your changes in the Edit tab will be overwritten, because the SQL in the Design tab will be reconstructed. If you select ‘No’ then the SQL in the Edit tab will remain intact and shall be used as the final SQL.