In addition to Weibo, there is also WeChat
Please pay attention
WeChat public account
Shulou
2025-03-31 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Database >
Share
Shulou(Shulou.com)06/01 Report--
1. Delete table drop
1.1 execute drop table table_name statement
The drop tables are placed in the user Recycle Bin (user_recyclebin) without being deleted directly, and the tables in the Recycle Bin can be restored. Get the deleted table information by querying the Recycle Bin user_recyclebin, and then use the following statement:
Flashback table user_recyclebin.object_name [user_recyclebin.original_name] to before drop [rename to new_table_name]
Restore the table in the Recycle Bin to its original name or specify a new name.
1.2 to delete a table completely, use the statement: drop table table_name purge
The statement says: do not put into the Recycle Bin, delete directly.
1.3 drop tables with foreign keys
Drop table table_name cascade constraints
-also known as cascading deletion, where related views and integrity constraints are deleted.
2. Delete the data in the table
2.1 delete
The delete operation applies to deleting some of the data in the table, but not all of the data. If you delete all rows in the table using delete, although the data in the table is deleted, the high water mark alone will not be released.
2.2 the truncate operation deletes all the information in the table, sets the high water mark to 0, and truncates the relevant indexes on the table.
Truncate table table_name
Truncate does not support rollback
You cannot truncate a table with a foreign key. If you want to delete it, cancel the foreign key first, and then delete it.
After truncate table, it is possible that the tablespace is still not freed.
You can release it using the following statement:
alter table table_name deallocate UNUSED KEEP 0
Alter table emp deallocate UNUSED KEEP 0
Or when you clear the data, reclaim the storage space as well:
TRUNCATE TABLE table_name DROP (REUSE) STORAGE
For example: truncate table test1 DROP STORAGE
Note: this blog is a summary of a number of blog posts and Oracle professional documents, and after my verification and summary, if there is any infringement, please contact me to indicate.
Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.
Views: 0
*The comments in the above article only represent the author's personal views and do not represent the views and positions of this website. If you have more insights, please feel free to contribute and share.
Continue with the installation of the previous hadoop.First, install zookooper1. Decompress zookoope
"Every 5-10 years, there's a rare product, a really special, very unusual product that's the most un
© 2024 shulou.com SLNews company. All rights reserved.