其實truncate很容易理解 主要是在多次創表過程中寫成truecate 加深一下印象

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.00 sec)

mysql> create database feiyu;
Query OK, 1 row affected (0.00 sec)

mysql> use feiyu;
Database changed
mysql>
mysql>
mysql>
mysql> create table `one`(
    -> id int unsigned not null auto_increment primary key,
    -> `username` varchar(50) not null,
    -> `password` varchar(32) not null,
    -> `age` int not null
    -> )engine=myisam default charset=utf8;
Query OK, 0 rows affected (0.00 sec)

mysql> desc one;
+----------+------------------+------+-----+---------+----------------+
| Field    | Type             | Null | Key | Default | Extra          |
+----------+------------------+------+-----+---------+----------------+
| id       | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| username | varchar(50)      | NO   |     | NULL    |                |
| password | varchar(32)      | NO   |     | NULL    |                |
| age      | int(11)          | NO   |     | NULL    |                |
+----------+------------------+------+-----+---------+----------------+
4 rows in set (0.01 sec)

mysql> insert into one (username,password,age) values('zhang1',123,25),('zhang2'
,123,24);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> insert into one (username,password,age) values('zhang3',123,25),('zhang4'
,123,24);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> insert into one (username,password,age) values('zhang5',123,25),('zhang6'
,123,24);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from one;
+----+----------+----------+-----+
| id | username | password | age |
+----+----------+----------+-----+
|  1 | zhang1   | 123      |  25 |
|  2 | zhang2   | 123      |  24 |
|  3 | zhang3   | 123      |  25 |
|  4 | zhang4   | 123      |  24 |
|  5 | zhang5   | 123      |  25 |
|  6 | zhang6   | 123      |  24 |
+----+----------+----------+-----+
6 rows in set (0.00 sec)

mysql> delete from one order by id desc limit 6;
Query OK, 6 rows affected (0.00 sec)              //6條記錄全部被刪

mysql> insert into one (username,password,age) values('zhang1',123,25),('zhang2'
,123,24);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from one;
+----+----------+----------+-----+
| id | username | password | age |                 //重新插入後 id=7  id=8 也就是說id沒有
+----+----------+----------+-----+
|  7 | zhang1   | 123      |  25 |                 //清空
|  8 | zhang2   | 123      |  24 |
+----+----------+----------+-----+
2 rows in set (0.00 sec)

mysql> truncate  one;
Query OK, 0 rows affected (0.00 sec)

mysql> insert into one (username,password,age) values('zhang1',123,25),('zhang2'
,123,24);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from one;
+----+----------+----------+-----+
| id | username | password | age |
+----+----------+----------+-----+
|  1 | zhang1   | 123      |  25 |               //truncate  會清空所有表資料 id也是從0 
|  2 | zhang2   | 123      |  24 |               //開始 
+----+----------+----------+-----+
2 rows in set (0.00 sec)