FROM What does " kích thước "trong int (kích thước) của MySQL nghĩa là gì?
mysql> create table a ( a tinyint );
Query OK, 0 rows affected (0.29 sec)
mysql> show columns from a;
+-------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| a | tinyint(4) | YES | | NULL | |
+-------+------------+------+-----+---------+-------+
1 row in set (0.26 sec)
mysql> alter table a change a a tinyint(1);
Query OK, 0 rows affected (0.09 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> insert into a values (100);
Query OK, 1 row affected (0.00 sec)
mysql> select * from a;
+-----+
| a |
+-----+
| 100 |
+-----+
1 row in set (0.00 sec)
2 Some code to better explain what I described so clumsily.
mysql> create table b ( b int (4));
Query OK, 0 rows affected (0.25 sec)
mysql> insert into b values (10000);
Query OK, 1 row affected (0.00 sec)
mysql> select * from b;
+-------+
| b |
+-------+
| 10000 |
+-------+
1 row in set (0.00 sec)
mysql> alter table b change b b int(11);
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from b;
+-------+
| b |
+-------+
| 10000 |
+-------+
1 row in set (0.00 sec)
mysql> alter table b change b b int(11) zerofill;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from b;
+-------------+
| b |
+-------------+
| 00000010000 |
+-------------+
1 row in set (0.00 sec)
mysql> alter table b change b b int(4) zerofill;
Query OK, 1 row affected (0.08 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from b;
+-------+
| b |
+-------+
| 10000 |
+-------+
1 row in set (0.00 sec)
mysql> alter table b change b b int(6) zerofill;
Query OK, 1 row affected (0.01 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from b;
+--------+
| b |
+--------+
| 010000 |
+--------+
1 row in set (0.00 sec)
