是的，DELETE比较慢，TRUNCATE比较快。为什么?

DELETE必须读取记录，检查约束，更新块，更新索引，并生成重做/撤销。所有这些都需要时间。

TRUNCATE只是在数据库中为表(High Water Mark)调整一个指针，然后!数据不见了。

这是Oracle特有的，AFAIK。

DELETE 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. Note that this operation will cause all DELETE triggers on the table to fire. TRUNCATE TRUNCATE removes all rows from a table. The operation cannot be rolled back and no triggers will be fired. As such, TRUCATE is faster and doesn't use as much undo space as a DELETE. DROP 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. 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.

来自:http://www.orafaq.com/faq/difference_between_truncate_delete_and_drop_commands

并不是说截断不记录SQL Server中的任何内容。truncate不记录任何信息，但它记录您触发truncate的表的数据页的释放。

如果在开始时定义事务，则可以回滚被截断的记录，回滚后可以恢复被截断的记录。但不能在提交截断事务后从事务日志备份中恢复截断记录。

truncate和delete的区别如下:

+----------------------------------------+----------------------------------------------+
|                Truncate                |                    Delete                    |
+----------------------------------------+----------------------------------------------+
| We can't Rollback after performing     | We can Rollback after delete.                |
| Truncate.                              |                                              |
|                                        |                                              |
| Example:                               | Example:                                     |
| BEGIN TRAN                             | BEGIN TRAN                                   |
| TRUNCATE TABLE tranTest                | DELETE FROM tranTest                         |
| SELECT * FROM tranTest                 | SELECT * FROM tranTest                       |
| ROLLBACK                               | ROLLBACK                                     |
| SELECT * FROM tranTest                 | SELECT * FROM tranTest                       |
+----------------------------------------+----------------------------------------------+
| Truncate reset identity of table.      | Delete does not reset identity of table.     |
+----------------------------------------+----------------------------------------------+
| It locks the entire table.             | It locks the table row.                      |
+----------------------------------------+----------------------------------------------+
| Its DDL(Data Definition Language)      | Its DML(Data Manipulation Language)          |
| command.                               | command.                                     |
+----------------------------------------+----------------------------------------------+
| We can't use WHERE clause with it.     | We can use WHERE to filter data to delete.   |
+----------------------------------------+----------------------------------------------+
| Trigger is not fired while truncate.   | Trigger is fired.                            |
+----------------------------------------+----------------------------------------------+
| Syntax :                               | Syntax :                                     |
| 1) TRUNCATE TABLE table_name           | 1) DELETE FROM table_name                    |
|                                        | 2) DELETE FROM table_name WHERE              |
|                                        |    example_column_id IN (1,2,3)              |
+----------------------------------------+----------------------------------------------+

SQL server中删除与截断的总结 完整文章请点击这个链接:http://codaffection.com/sql-server-article/delete-vs-truncate-in-sql-server/

摘自dotnet mob文章:删除Vs截断SQL Server

通过发出TRUNCATE TABLE语句，您将指示SQL Server删除表中的每条记录，而不进行任何日志记录或事务处理。