When it comes to deleting data from a database table, there are two main commands that can be used: DELETE and TRUNCATE. While both commands can be used to remove data from a table, there are some key differences between them. In this article, we'll explore the differences between DELETE and TRUNCATE, as well as when each command should be used. DELETE is a DML command, while TRUNCATE is a DDL command.
DML stands for Data Manipulation Language, and DDL stands for Data Definition Language. DML commands are used to manipulate data within a database table, while DDL commands are used to define the structure of a database table. The main difference between DELETE and TRUNCATE is that DELETE can be used to delete specific rows from a table, while TRUNCATE removes all rows from a table. DELETE creates an entry for each deletion in the transaction log, while TRUNCATE demaps pages and creates an entry for de-mapping pages in the transaction log.
DELETE can be used to delete all rows or just a subset of rows from a table or cluster. On the other hand, TRUNCATE only applies to tables or to the entire cluster. Additionally, DELETE can be applied to tables and tables within a cluster, while TRUNCATE only applies to tables or to the entire cluster. TRUNCATE removes all rows from a table without maintaining the integrity of the table.
This means that TRUNCATE is faster and doesn't use as much space to undo as DELETE. However, TRUNCATE transactions cannot be undone in database engines such as MySQL and Oracle. Table-level locks will be added when truncating, which means that other users will not be able to access the table until the operation is complete. Additionally, rows removed by the TRUNCATE TABLE statement cannot be restored and the WHERE clause cannot be specified in the TRUNCATE statement. If you want to quickly delete all the rows in a table, and you're sure you want to, and you don't have foreign keys in the tables, then TRUNCATE will be faster than DELETE.
However, if you need to delete specific data or maintain integrity compliance mechanisms, then DELETE should be used instead of TRUNCATE. In summary, DELETE is used to delete specific data from a table while maintaining integrity compliance mechanisms, while TRUNCATE is used to remove all data from a table without maintaining the integrity of the table. Additionally, DELETE operations can be undone (undo), whereas DROP and TRUNCATE operations cannot be undone.