I have summarized main difference between Truncate and Delete command in Oracle.
| Truncate | Delete |
| DDL command | DML command |
| Cannot be rolled back | Can be rolled back |
| Associated with commit | Need to commit explicitly after |
| Will not fire trigger associated with the table | Will fire trigger associated with the table |
| Cannot be used with where clause | Where clause can be used |
| Reset the high water mark | No association with high water mark |
| Generally executes faster than delete | Generally executes slower than truncate |
| Cannot run truncate for a parent table with constraints | Delete can be applied after deleting the child records |
Note that TRUNCATE table has two variants
1. Truncate table table_name;
or
Truncate table table_name drop storage;
(drop storage is by default)
Here Truncate reset the high water mark
2. Truncate table table_name REUSE storage;
In this case Oracle will not reset the high water mark and same storage space will allocated for new entries in future.
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4 responses to “Difference between DELETE and TRUNCATE in Oracle”
Summary
Delete
1.DML data can be recovered by rollback before commit
2.Remove any subset of data
3.Delete is slower when table have numerous indexes and triggers
4.DML triggers fire for delete mthod
5.data can be recovered after commit by flashback method
6.high water mark will remain the same
7.data deleted info capture with returning clause
8. you can not delete data if function based index is invalid
9. can not delete data from complex views.
10. Space is not freed
Truncate
1.Truncated Data can not be recoverd but truncated data is also logged
2.truncate all or partition or subpartition data.
3. truncate is faster as no logs we have to maintain ,no trigger firing
4. reset the high water mark , space is released except reuse method
5. can not truncate table indivisually if it is part of cluster
6. can not truncate table with referential integerity constraint enable
7. if table is not empty unuseable indexes become useable
8. if domain index on table is invalid or in_progess state then we can not truncate the table
8.we can not truncate a simple view , we can truncate MV but not simple view
11 main Differences between Delete and Truncate in sql server
http://www.webcodeexpert.com/2013/03/difference-between-delete-and-truncate.html
I’ve worked a lot with Oracle and have started working more with Teradata recently. Interestingly enough, Teradata has no TRUNCATE command. There is a DELETE ALL command vs. just the regular delete but I am not 100% sure if DELETE ALL is exactly equivalent to TRUNCATE in Oracle.
Thanks for the comment
Thanks for the comment