Difference between DROP and Truncate

Several SQL commands can be used to alter or remove data from a database. The two most frequently used commands are TRUNCATE and DROP. These two commands have the same purpose − to remove data from a database − but they operate and behave differently. Anybody working with SQL databases has to understand the distinction between DROP and TRUNCATE.

A complete table, including its structure, indexes, and data, can be deleted with the DROP command. Once performed, it is a permanent action that cannot be reversed. On the other hand, a table's structure and indexes are preserved when all the data is removed from it using the TRUNCATE command. It is a transient action that can be reversed if necessary by using a transaction log.

What is DROP Command?

A database object, such as a table, index, or view, can be deleted from the database together with all of its related data and metadata by using the DROP command in SQL. The database object is permanently deleted and cannot be recovered when the DROP command is used. Depending on the object being dropped, the syntax for the DROP command differs. When employing the DROP command, it's crucial to use caution since if used improperly, it can result in unwanted repercussions. For instance, dropping a table may result in the loss of all data it contains. Before using the DROP command, it is advised as best practise to create a backup of the database.

DROP Command – Advantages

• Effective data management − The "drop" command can aid in effective data management by eliminating extraneous data, freeing up storage space, and enhancing system performance.

• Enhanced security − By deleting critical data using the "drop" command, the risk of data breaches and unauthorised access to information is reduced.

• Simple data deletion − Deleting data that is no longer required or is obsolete is simple and quick with the "drop" command.

DROP Command – Disadvantages

• Possible deletion − The possibility of unintentional deletion is one of the "drop" command's biggest drawbacks.

• Action that cannot be undone − The "drop" command permanently deletes data from the system or software.

• Negative Impacts − Using the "drop" command to remove a crucial piece of data or code can have a detrimental effect on how well an application or system functions, resulting in errors, crashes, and other problems.

What is TRUNCATE Command?

With the SQL TRUNCATE command, all rows from a table can be deleted while the table's structure, metadata, and indexes are still present. In contrast to the DROP command, TRUNCATE just deletes the data from the table, not the database itself or any related metadata.

The data pages used to store the table's data are reallocated when the TRUNCATE command is used, and the table's identity value is also reset. This indicates that the identity value for the table's initial insert operation will be 1.

The TRUNCATE command is a DDL (Data Definition Language) operation, not a DML (Data Manipulation Language) operation, which is crucial to keep in mind. As opposed to other techniques for deleting data from a database, TRUNCATE does not create any transaction logs, which can increase performance.

The TRUNCATE command is a potentially hazardous operation, so it is vital to use caution when performing it. TRUNCATE is an irreversible operation in contrast to DELETE, which can be reversed via a transaction log. Because of this, it is advised to create a backup of the table before running the TRUNCATE command.

TRUNCATE Command – Advantages

• Faster than DELETE − When working with huge tables, the TRUNCATE command is significantly quicker than the DELETE command. This is because the DELETE command removes each row individually, but the TRUNCATE command merely removes the data from the table.

• Reset the identity column − The TRUNCATE command resets the table's identity column, enabling you to start the primary key values from scratch once more.

• Reduces the size of the transaction log − The TRUNCATE command deletes all of the data from the table and reallocates the data pages it utilised, freeing up disc space.

TRUNCATE Command – Disadvantages

• Action that cannot be undone − The TRUNCATE command cannot be undone. There is no method to get back data that has been deleted using it from a table. If you mistakenly truncate a table or need to preserve a record of the lost data, this could be a drawback.

• WHERE is absent − The TRUNCATE command deletes all the data in the table, which can be a drawback if you only want to erase particular rows. This is in contrast to the DELETE command, which allows you to enter a WHERE clause to limit the rows to delete.

• Resets all constraints − The TRUNCATE command resets all of the table's constraints, including foreign key restrictions. You might need to manually recreate the foreign key restrictions if you truncate a table that is used as a reference by other tables.

DROP Vs TRUNCATE

The following table highlights the major differences between DROP and TRUNCATE −

DROP	TRUNCATE
The table definition and its data are deleted using the SQL DROP command.	All of the data in the table is deleted using the SQL TRUNCATE command.
The tablespace is released from the RAM by this query.	The tablespace is not released from the storage by the TRUNCATE query.
The DROP command doesn't have a view for the table.	There is a tabular view available with the Truncate command.
The DROP command will automatically remove the integrity restrictions from the table.	This command's integrity restrictions won't be relaxed.
The removed space is not utilised in the DROP query.	Although less than the DELETE command, the removed space is still used.
Although the DROP query deletes data quickly, there are numerous issues.	In SQL, the TRUNCATE query executes more quickly than the DROP query.

Conclusion

To sum up, both the DROP and TRUNCATE commands are used to delete data from a SQL database, but they serve different purposes and have different functionality.

While the TRUNCATE command only removes the data from a table while leaving the table's structure, metadata, and indexes intact, the DROP command permanently eliminates a database object along with all of its associated data and metadata. While often faster than DROP, the TRUNCATE command is a potentially hazardous operation that cannot be reversed.

To maintain the database's integrity and performance, it's critical to comprehend how these instructions differ from one another and to use them properly.