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# 03 truncate 和 delete

删除表信息的方式有两种：

```sql
truncate table table_name;
delete * from table_name;
```

`truncate` 操作中的 table 可以省略，`delete` 操作中的 `*` 可以省略。

`truncate` 是清空，`delete` 是删除。

`truncate` 和 `delete` 清空表数据的区别：

1. `truncate` 是整体删除（速度较快），`delete` 是逐条删除（速度较慢）；
2. `truncate` 不写服务器 log，`delete` 写服务器 log，也就是 `truncate` 效率比 `delete` 高的原因；
3. `truncate` 不激活 trigger（触发器），但是会重置 Identity（标识列、自增字段），相当于自增列会被置为初始值，又重新从 1 开始记录，而不是接着原来的 ID 数。而 `delete` 删除以后，identity 依旧是接着被删除的最近的那一条记录 ID 加 1 后进行记录。如果只需删除表中的部分记录，只能使用 DELETE 语句配合 where 条件；


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