What is the difference between delete and truncate in mysql

It removes the complete row from the table and produces the count of deleted rows. We need the delete permission on the target table to execute this command. It clarifies that we have a backup of our database before executing this command because we cannot recover the deleted records using this query. Therefore, the database backups allow us to restore the data whenever we need it in the future. The truncate statement is a DDL or data definition language command used to removes complete data from the table without removing the table structure.

After executing this command, we cannot rollback the deleted data because the log is not maintained while performing this operation. The truncate command deallocates the pages instead of rows and makes an entry for the deallocating pages instead of rows in transaction logs. This command locks the pages instead of rows; thus, it requires fewer locks and resources. Note that we cannot use the truncate statement when a table is referenced by a foreign key or participates in an indexed view.

In this article, we have made a comparison between delete and truncate statement. JavaTpoint offers too many high quality services. Mail us on [email protected] , to get more information about given services.

Please mail your requirement at [email protected] Duration: 1 week to 2 week. This effectively means that it is essential to be careful while giving the truncate command in SQL as all the rows in the entire table will be deleted quite fast, and the information may not be logged in about every row that is removed. The data recovery process is long and cumbersome, requires advanced coding and may lead to irrecoverable data loss. It is essential to know that using the truncate command in SQL locks the table on which it is used.

This, in turn, means that the table will be closed for use for all concurrent users if any. Thus, be careful while using this command as it will make the queried table entirely inaccessible for other shared users along with yourself. In case the WHERE condition is not given, then all the rows contained in the specific table will get deleted. If you are wondering about the delete and truncate difference regarding when to use this command, then do know that the DELETE command can be effectively used for removing the records from any given database - either all records or designated rows - as per the usage of the WHERE clause.

In case you choose to drop a given table from your database, then the DROP command will remove the complete table structure after deleting each of its rows. A table once dropped in this manner cannot be retrieved. Also, as no reference to the dropped table remains valid after this command has been fired, it is vital to use the DROP statement carefully. Once a table has been dropped, all relationships with other objects and tables will be automatically dropped and will become invalid.

Along with the integrity constraints, access privileges and additional references will also get dropped. I've highlighted Oracle-specific features, and hopefully the community can add in other vendors' specific difference also.

Differences that are common to most vendors can go directly below the headings, with differences highlighted below. Truncate can therefore not be rolled back, and a failure in the truncate process will have issued a commit anyway. The high water mark is reset. When a table is partitioned, the individual partitions can be truncated in isolation, thus a partial removal of all the table's data is possible.

Delete can be applied to tables and tables inside a cluster. Truncate applies only to tables or the entire cluster. May be Oracle specific. Delete does not affect the data object id, but truncate assigns a new data object id unless there has never been an insert against the table since its creation Even a single insert that is rolled back will cause a new data object id to be assigned upon truncation.

Flashback works across deletes, but a truncate prevents flashback to states prior to the operation. Delete generates a small amount of redo and a large amount of undo. Truncate generates a negligible amount of each. A truncate cannot be applied when an enabled foreign key references the table.

Treatment with delete depends on the configuration of the foreign keys. Truncate requires an exclusive table lock, delete requires a shared table lock. Hence disabling table locks is a way of preventing truncate operations on a table.

The DROP command removes a table from the database. All the tables' rows, indexes and privileges will also be removed. No DML triggers will be fired. The operation cannot be rolled back. The operation cannot be rolled back and no triggers will be fired. Table level lock will be added when Truncating. Row level lock will be added when deleting. The speed advantage of truncate over delete should be obvious. That advantage ranges from trivial to enormous, depending on your situation.

However, I've seen truncate unintentionally break referential integrity, and violate other constraints. The power that you gain by modifying data outside a transaction has to be balanced against the responsibility that you inherit when you walk the tightrope without a net.

Below are the differences between the two:. And this is the reason why rows deleted by truncate could not be rollbacked. Here is the very good link relevant to the topic. All of that takes time. You can rollback committed transaction. The related information below is from a blog post :. While working on database, we are using Delete and Truncate without knowing the differences between them.

In this article we will discuss the difference between Delete and Truncate in Sql. Note: Delete and Truncate both can be rolled back when used with Transaction. If Transaction is done, means committed then we can not rollback Truncate command, but we can still rollback Delete command from Log files, as delete write records them in Log file in case it is needed to rollback in future from log files.

If you have a Foreign key constraint referring to the table you are trying to truncate, this won't work even if the referring table has no data in it. This can be got around by temporarily disabling the foreign key constraint s to the table. Delete table is a logged operation.

So the deletion of each row gets logged in the transaction log, which makes it slow. Truncate table also deletes all the rows in a table, but it won't log the deletion of each row instead it logs the deallocation of the data pages of the table, which makes it faster.

And one of the reason is locks used by either statements. If no seed was defined, the default value 1 is used. If the DELETE removes multiple rows, and any one of the removed rows violates a trigger or constraint, the statement is canceled, an error is returned, and no rows are removed. Just make sure you explain it properly to the Interviewer or it might cost you the job. View All. Arjun Panwar Updated date Aug 31, In this tutorial, I am going to explain the delete, truncate, and drop statements of MySQL with various examples.

Then use:. After truncate this table do not contains any fields but it show in our database by using the following command. DROP statement is used to delete the table structure with all the data.