PRESERVE TABLE Clause This clause lets you retain the materialized view container table and its contents after the materialized view object is dropped. The resulting table has the same name as the dropped materialized view. 保留表条款
此子句允许在物理化视图对象被删除后，保留物化视图容器表及其内容。 生成的表与删除的实例化视图具有相同的名称。
drop materialized view MV_jobs PRESERVE TABLE后，USER_MVIEWS不见了MV_jobs,但是user_tables、dba_objects、dba_segments还有MV_jobs，select * from MV_jobs不会报错 drop materialized view MV_jobs后USER_MVIEWS、user_tables、dba_objects、dba_segments都不见了MV_jobs，select * from MV_jobs不会报错
conn hr/hr create materialized view MV_jobs refresh complete on demand as select * from jobs; drop materialized view MV_jobs PRESERVE TABLE; select * from MV_jobs;--有结果
