How to Rank Customers by Age and Gender in MySQL?

Ranking Customers in MySQL: A Practical Guide

MySQL doesn't offer a built-in rank function, requiring custom queries for ranking customers by age and gender. This guide demonstrates a solution using a user-defined variable for efficient ranking.

The Query:

This query utilizes a variable to assign ranks:

<code class="language-sql">SELECT    first_name,
          age,
          gender,
          @curRank := @curRank + 1 AS rank
FROM      person p, (SELECT @curRank := 0) r
ORDER BY  age;</code>

The clever part is the (SELECT @curRank := 0) r subquery. This elegantly initializes the ranking variable @curRank, eliminating the need for a separate SET statement.

Illustrative Example:

Let's consider a sample person table:

<code class="language-sql">CREATE TABLE person (id int, first_name varchar(20), age int, gender char(1));

INSERT INTO person VALUES (1, 'Bob', 25, 'M');
INSERT INTO person VALUES (2, 'Jane', 20, 'F');
INSERT INTO person VALUES (3, 'Jack', 30, 'M');
INSERT INTO person VALUES (4, 'Bill', 32, 'M');
INSERT INTO person VALUES (5, 'Nick', 22, 'M');
INSERT INTO person VALUES (6, 'Kathy', 18, 'F');
INSERT INTO person VALUES (7, 'Steve', 36, 'M');
INSERT INTO person VALUES (8, 'Anne', 25, 'F');</code>

Query Results:

Executing the query yields the following ranked customer data:

<code>+------------+------+--------+------+
| first_name | age  | gender | rank |
+------------+------+--------+------+
| Kathy      |   18 | F      |    1 |
| Jane       |   20 | F      |    2 |
| Nick       |   22 | M      |    3 |
| Bob        |   25 | M      |    4 |
| Anne       |   25 | F      |    5 |
| Jack       |   30 | M      |    6 |
| Bill       |   32 | M      |    7 |
| Steve      |   36 | M      |    8 |
+------------+------+--------+------+</code>

This clearly shows the customers ranked by age. To incorporate gender into the ranking, simply adjust the ORDER BY clause to include gender as a secondary sorting criteria (e.g., ORDER BY age, gender).

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