What is the difference between drop and delete

The difference between drop and delete: 1. Function and purpose; 2. Operation object; 3. Reversibility; 4. Space release; 5. Execution speed and efficiency; 6. Logging; 7. Other database commands Interaction; 8. Persistence of effects; 9. Syntax and execution; 10. Triggers and constraints; 11. Transaction processing. Detailed introduction: 1. Function and purpose. DROP is mainly used to delete data structure, including internal data content. DELETE is mainly used to delete data content. It does not delete data structure and only affects the data in the table, etc.

DROP and DELETE are two commands commonly used in database management. They are in terms of function, purpose, operation object, reversibility, space release, execution speed and efficiency. There are clear differences in interaction with other commands, persistence of effects, syntax and execution, triggers and constraints, and logging.

1. Function and purpose:

• DROP is mainly used to delete data structures, including internal data content, such as deleting databases or data tables. .

• DELETE is mainly used to delete data content. It does not delete the data structure and only affects the data in the table.

2. Operation object:

• The operation object of DROP can be a database or a data table in the database.

• DELETE's operation object can only be the data table in the database.

3. Reversibility:

• DROP operation is not placed in the rollback segment and cannot be rolled back. trigger.

• The DELETE operation will be placed in the rollback segment, will take effect after the transaction is submitted, and the corresponding trigger will be triggered during execution.

4. Space release:

• The DROP operation will release the space occupied by the table.

• DELETE operation will not release space.

5. Execution speed and efficiency:

• DROP operations are usually immediately visible and will release space immediately .

• DELETE operation may be slower than DROP because it does not release space immediately and may require more internal processing.

6. Logging:

• DROP operations are usually not recorded in the transaction log because it involves Delete an entire table or database structure.

• DELETE operations are usually recorded in the transaction log, which facilitates data recovery and transaction rollback.

7. Interaction with other database commands:

• DROP is a more basic database command and cannot be interacted with other database commands. used together with the command.

• DELETE can be used with the WHERE clause to delete records that meet certain conditions; it can also be used with the LIMIT clause to limit the number of rows deleted.

8. Durability of the impact:

• DROP operation completely removes data and structures from the database. Deleted data cannot be recovered.

• DELETE operation only temporarily deletes data, the data is still stored in the database, just marked as "deleted" until the transaction is committed or a certain time period is exceeded. This means that in some cases, deleted data can still be recovered.

9. Syntax and execution:

• DROP usually requires more complex syntax because it involves deleting the entire Table or database structure.

• DELETE usually uses a simpler syntax and only requires specifying the table to be deleted and possible conditions.

10. Triggers and constraints:

• DROP will delete all related triggers and constraints.

• DELETE may trigger related triggers and constraints when executed.

11. Transaction processing:

• DROP operation is atomic and cannot be executed in a transaction. Once a DROP is performed, either all related tables and structures are deleted, or nothing is deleted.

• DELETE operations can be executed within a transaction, which means that if the transaction fails, the changes made can be undone.

In summary, "DROP" and "DELETE" each have their own uses and characteristics in database management. You need to choose the appropriate command to perform the corresponding operation according to specific needs. Use caution when using it and make sure you understand its meaning and impact to avoid unnecessary data loss or other problems.

The above is the detailed content of What is the difference between drop and delete. For more information, please follow other related articles on the PHP Chinese website!