MySql: Tinyint (2) vs tinyint(1) - what is the difference?

I knew boolean in mysql as tinyint (1).

Today I see a table with defined an integer like tinyint(2), and also others like int(4), int(6) ...

What does the size means in field of type integer and tinyint ?

 Answers

It means display width

Whether you use tinyint(1) or tinyint(2), it does not make any difference.

I always use tinyint(1) and int(11), I used several mysql clients (navicat, sequel pro).

It does not mean anything AT ALL! I ran a test, all above clients or even the command-line client seems to ignore this.

But, display width is most important if you are using ZEROFILL option, for example your table has following 2 columns:

A tinyint(2) zerofill

B tinyint(4) zerofill

both columns has the value of 1, output for column A would be 01 and 0001 for B, as seen in screenshot below :)

---

mysql> CREATE TABLE tin3(id int PRIMARY KEY,val TINYINT(10) ZEROFILL);
Query OK, 0 rows affected (0.04 sec)

mysql> INSERT INTO tin3 VALUES(1,12),(2,7),(4,101);
Query OK, 3 rows affected (0.02 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM tin3;
+----+------------+
| id | val        |
+----+------------+
|  1 | 0000000012 |
|  2 | 0000000007 |
|  4 | 0000000101 |
+----+------------+
3 rows in set (0.00 sec)

mysql>

mysql> SELECT LENGTH(val) FROM tin3 WHERE id=2;
+-------------+
| LENGTH(val) |
+-------------+
|          10 |
+-------------+
1 row in set (0.01 sec)


mysql> SELECT val+1 FROM tin3 WHERE id=2;
+-------+
| val+1 |
+-------+
|     8 |
+-------+
1 row in set (0.00 sec)