Difference between:
- Delete & Truncate
- Table & View
- Constraints & Triggers
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Answer Posted / amrish kumar
The DELETE command is used to remove rows from a table. A
WHERE clause can be used to only remove some rows. If no
WHERE condition is specified, all rows will be removed.
After performing a DELETE operation you need to
COMMIT or ROLLBACK the transaction to make the change
permanent or to undo it.
TRUNCATE removes all rows from a table. The operation cannot
be rolled back. As such, TRUCATE is faster and doesn't use
as much undo space as a DELETE.
DROP and TRUNCATE are DDL commands, whereas DELETE is a DML
command. Therefore DELETE operations can be rolled back
(undone), while DROP and TRUNCATE operations cannot be
rolled back.
Table is a basic unit of data storage in an oracle database.
It holds all user accessible data.
View is a virtual table
- It can be created on a table or another view.
- It is just like a window through which we can access or
change base table data.
- It does contain data of its own. It always takes data from
its base table.
- It is stored as a query in data dictionary.Whenever you
query a view it gets data from its based table using this query.
Constraints are great at maintaining database integrity for
database fields and relationships between database tables.
Triggers are great for checking past vs. current values and
making decisions based on that data.
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