display numbers with zero pad

Question

I have some data stored as an unsigned tinyint. When displaying it I want it to be zero padded only if it is 1 digit in length. I have issues with LPAD(CAST(NUMBER AS CHAR CHARSET UTF8),2,'0') when I have three digit long numbers. How do I get what I'm looking for?

Example of data in table:

NUMBER
1
2
3
...
10
11
...
101
102

What I currently get when running with LPAD

LPAD_NUMBER
01
02
03
...
10
11
...
10
10

What I want

UNKNOWN
01
02
03
...
10
11
...
101
102

SOLUTION I USED

select case 
    when number between 0  and 9 then
        LPAD(CAST(number AS CHAR CHARSET UTF8), 2, '0')
    else
        CAST(number AS CHAR CHARSET UTF8)
    end as newNum;

This gets me what I'm looking for and is based off of the accepted answer.

Answer 1

You can use a case expression:

select case when number between 0 and 9 then '0' else '' end 
    || number as n 
from t;

Note that || is the sql-standard operator for string concatenation. Unless properly configured MySQL will treat || as logical OR. This behavior is determined by the setting PIPES_AS_CONCAT. You can also enable this and other sane settings with ANSI. You can see what settings you have with:

select @@sql_mode;

It can be changed using:

set @@sql_mode=@@sql_mode || ',PIPES_AS_CONCAT';

or by modifying the config file

However this is purely presentation so I think you should do the formatting of the result in the application instead.

Answer 2

Declaring this way:

number INT(5) ZEROFILL

will pad number to at least 5 digits with leading zeros. This is the only use for (5).

Example:

Showing that zeros are displayed:

CREATE TABLE `zips` (
  `id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
  `zip` mediumint(5) unsigned zerofill NOT NULL,
  `state` char(2) DEFAULT NULL,
...
  PRIMARY KEY (`id`),
  KEY `zip` (`zip`),
  KEY `state` (`state`,`county`,`city`)
) ENGINE=InnoDB AUTO_INCREMENT=79992 DEFAULT CHARSET=latin1 ;

mysql> SELECT zip, CONCAT('A-', zip), city
             FROM zips  WHERE zip < 11000  LIMIT 5;
+-------+-------------------+----------------------+
| zip   | CONCAT('A-', zip) | city                 |
+-------+-------------------+----------------------+
| 00501 | A-00501           | HOLTSVILLE           |
| 00501 | A-00501           | I R S SERVICE CENTER |
| 00544 | A-00544           | HOLTSVILLE           |
| 00544 | A-00544           | IRS SERVICE CENTER   |
| 00601 | A-00601           | ADJUNTAS             |
+-------+-------------------+----------------------+
5 rows in set (0.00 sec)

Showing that a too-big value works 'right':

mysql> INSERT INTO zips (zip) VALUES (123456);
Query OK, 1 row affected, 9 warnings (0.00 sec)
-- (The warnings relate to failing to provide values for other columns.)

mysql> SELECT zip, city  FROM zips  ORDER BY zip DESC  LIMIT 5;
+--------+-----------+
| zip    | city      |
+--------+-----------+
| 123456 |           |
|  99950 | KETCHIKAN |
|  99950 | KASAAN    |
|  99950 | EDNA BAY  |
|  99929 | WRANGELL  |
+--------+-----------+
5 rows in set (0.00 sec)