Sorting Alpha Numeric Data in MySQL

Methods to Sort Alpha-
numeric Data in MySQL
Abdul Rahman Sherzad
Lecturer at Computer Science faculty
Herat University, Afghanistan

ORDER BY Keyword
• In SQL, the ORDER BY keyword is used to sort the result-set in
ascending (ASC) or descending (DESC) order by some specified
column/columns.
• It works great for most of the cases.
• However, for alphanumeric data, it may not return the result-set
that you will be expecting.
• This presentation explains how this can be addressed using
different techniques.
2

Scenario I: Table Structure and Test Data
Table Structure
CREATE TABLE warnings
(
id INT NOT NULL
PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(50) NOT NULL,
due VARCHAR(20)
);
Test Data
INSERT INTO warnings
(name, due) VALUES
('Aaaaa', '10 days'),
('Baaaa', '1 days'),
('Ccccc', '2 days'),
('Ddddd', '12 days'),
('Eeeee', '20 days'),
('Fffff', '2 days'),
('Ggggg', '5 days'),
('Hhhhh', '3 days');
3

Scenario I: The Problem
• Assume there is a table named 'warnings' with the following
'due' and 'name' columns.
• The data for 'due' column is alphanumeric.
• A report is needed to display the data sorted by the 'due'
column. But, the result of the following query is not as it
is expected:
SELECT due, name FROM warnings
ORDER BY due ASC;
4

Solution #1: Identity Elements
5
• The number '0' in addition, and '1' in multiplication are
identity elements. An identity element is a number that
combines with other elements in a mathematical equation
but does not change them.
ORDER BY due + 0 ASC;
OR the following
ORDER BY due * 1 ASC;

Solution #2: CAST() function
6
• The CAST() function converts a value from
one datatype to another datatype.
• Using cast() function is another method to
address the mentioned problem as follow:
SELECT due, name
FROM warnings
ORDER BY CAST(due AS SIGNED) ASC;

Solution #3: Natural Sorting
7
• It is simple enough to accomplish natural
sorting in MySQL:
• First sort by length of the column,
• Then sort by the original column value.
SELECT due, name
FROM warnings
ORDER BY LENGTH(due) ASC, due ASC;
• NOTE: The ASC keyword can be omitted, as it is the DEFAULT.

This is not end of the story!
• The above Solution #1 and Solution #2 works only with alpha-numeric data
starts with numbers.
• The Solution #1 and Solution #2 do not work with alpha-numeric data ends
with numbers!
8

Scenario II: Table Structure and Test Data
Table Structure
CREATE TABLE tests
(
id INT NOT NULL
PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(50) NOT NULL,
score INT
);
Test Data
INSERT INTO tests
(name, score) VALUES
('Test 1', 10),
('Test 10', 5),
('Test 3', 10),
('Test 2', 4),
('Test 15', 5),
('Test 18', 10),
('Test 20', 5),
('Test 9', 10);
9

Scenario II: The Problem
10
• Assume there is a table named 'tests' with the
following two columns 'name' and 'score'.
• The data in the column 'name' are alpha-numeric
• but the numbers are at the end of the string.
• With such a structure, the above-mentioned
Solution #1 and Solution #2 do not work as
illustrated on next slide 

Solution #1 and Solution #2: Issue
11
• The following queries do not sort the result-sets
as it is expected:
• Solution #1:
SELECT name, score FROM tests
ORDER BY name + 0 ASC;
• Solution #2:
SELECT name, score
FROM tests
ORDER BY CAST(name AS UNSIGNED);

Solution #3: Natural Sorting
12
• The natural sorting works properly with
alpha-numeric data whether the numbers
are at the beginning, or at the end of the
string, as illustrated on this slide.
SELECT name, score
FROM tests
ORDER BY LENGTH(name) ASC, name ASC;

What about the following Scenario?
• What about mixture of data (a very rare case)
• alpha-numeric data with numbers at the beginning of the
string
• alpha-numeric data with numbers at the end of the string
• Only numeric data
• Only alphabetic data
13

Scenario III: Table Structure and Test Data
Table Structure
CREATE TABLE tests (
test VARCHAR(20) NOT NULL
);
Test Data
INSERT INTO tests
(test) VALUES
('A1'), ('A10'), ('A2’),
('1 day'), ('10 day'), ('2 day’),
('10'), ('1'), ('2’),
('Sherzad’),
('Abdul Rahman');
14

Scenario III: ORDER BY Keyword
15
SELECT test
FROM tests
ORDER BY test ASC;
NOTE: The ASC keyword can be omitted, as
it is the DEFAULT.

Scenario III: Identity Elements and
CAST() function
16
• Casting using Identity Elements
SELECT test FROM tests
ORDER BY test + 0 ASC;
• CAST() function
ORDER BY CAST(test AS UNSIGNED) ASC;
NOTE: The ASC keyword can be omitted, as it is the DEFAULT.

Scenario III: Identity Elements and
CAST() function
17
• To sort the data based on the numeric
values, simply use the following queries:
ORDER BY test + 0 ASC, test ASC;
• OR
ORDER BY CAST(test AS UNSIGNED) ASC,
test ASC;

Scenario III: Natural Sorting
18
SELECT test
FROM tests
ORDER BY LENGTH(test) ASC,
test ASC;

Summary
In most cases including alpha-numeric data
with numbers either at the beginning or at the
end of the string Natural Sorting method
works pretty well.
•First sort by length of the column,
•Then sort by the original column value.
In case there are different variations of data
in same column (which is very rare), different
methods can be picked e.g.
• The data can be sorted based on their numeric values as
illustrated on slide 17,
• The data can be sorted using Natural Sorting method,
• Or combination of other methods
19
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