Do SQL queries work in every database? I wouldn’t count on it. That’s why this article gives you several alternatives.
Want to let number or rank your query results? Let your database do the hard work for you.
Let’s say you have a team table in your database that stores the name and number of gold, silver, and bronze medals won for each team:
| team | ||||
|---|---|---|---|---|
| id | name | gold | silver | bronze |
| 1 | Taiwan #1 | 4 | 2 | 1 |
| 2 | There was an attempt | 0 | 0 | 0 |
| 4 | Team 4 Plays | 3 | 2 | 2 |
| 5 | Five Gals | 3 | 2 | 2 |
| 6 | Sixcess guaranteed | 5 | 4 | 1 |
| 7 | We ate nine | 0 | 6 | 3 |
| 8 | AMERICA F*** YEAH | 5 | 4 | 0 |
As you can see, this table is currently ordered by id. We can use the ORDER BY clause to request a version of this data that shows teams with the most gold, silver, and bronze medals first:
SELECT
name,
gold,
silver,
bronze
FROM
team
ORDER BY
gold DESC,
silver DESC,
bronze DESC;
+----------------------+------+--------+--------+
| name | gold | silver | bronze |
+----------------------+------+--------+--------+
| Sixcess guaranteed | 5 | 4 | 1 |
| AMERICA F*** YEAH | 5 | 4 | 0 |
| Taiwan #1 | 4 | 2 | 1 |
| Team 4 plays | 3 | 2 | 2 |
| Five Gals | 3 | 2 | 2 |
| We ate nine | 0 | 6 | 3 |
| There was an attempt | 0 | 0 | 0 |
+----------------------+------+--------+--------+
While this gives you all the information you need, it would be more convenient if the rows were also numbered. You could number them yourself, but why do that when you can do it just as easily using SQL?
The recommended way to number rows
There are two so-called window functions, ROW_NUMBER() and RANK(), that can be used to number rows in SQL output.
The first window function, ROW_NUMBER(), simply assigns a unique number from 1 to whatever the number of rows in the query result is. The snippet below shows how ROW_NUMBER() can be used to number teams. Note that the ORDER BY clause has been moved to ROW_NUMBER() OVER ().
This can be useful if the result is meant to represent a sequence or if you simply need a way to refer to each row that is not based on an actual ID.
SELECT
ROW_NUMBER() OVER (
ORDER BY
gold DESC,
silver DESC,
bronze DESC
) AS number,
name,
gold,
silver,
bronze
FROM
team;
+--------+----------------------+------+--------+--------+
| number | name | gold | silver | bronze |
+--------+----------------------+------+--------+--------+
| 1 | Sixcess guaranteed | 5 | 4 | 1 |
| 2 | AMERICA F*** YEAH | 5 | 4 | 0 |
| 3 | Taiwan #1 | 4 | 2 | 1 |
| 4 | Team 4 plays | 3 | 2 | 2 |
| 5 | Five Gals | 3 | 2 | 2 |
| 6 | We ate nine | 0 | 6 | 3 |
| 7 | There was an attempt | 0 | 0 | 0 |
+--------+----------------------+------+--------+--------+
The other window function, RANK(), ranks your rows using the ordering criteria that you define within the OVER () part. This is particularly useful when the results represent a list from best to worst (as in this example) from largest to smallest, smallest to largest, etc.
SELECT
RANK() OVER (
ORDER BY
gold DESC,
silver DESC,
bronze DESC
) AS rank,
name,
gold,
silver,
bronze
FROM
team;
+------+----------------------+------+--------+--------+
| rank | name | gold | silver | bronze |
+------+----------------------+------+--------+--------+
| 1 | Sixcess guaranteed | 5 | 4 | 1 |
| 2 | AMERICA F*** YEAH | 5 | 4 | 0 |
| 3 | Taiwan #1 | 4 | 2 | 1 |
| 4 | Team 4 plays | 3 | 2 | 2 |
| 4 | Five Gals | 3 | 2 | 2 |
| 6 | We ate nine | 0 | 6 | 3 |
| 7 | There was an attempt | 0 | 0 | 0 |
+------+----------------------+------+--------+--------+
ROW_NUMBER() in old versions of MySQL
ROW_NUMBER() should be widely supported by now. Nevertheless, there are still many older databases that do not support it yet. It wouldn’t surprise me if most of those are older versions of MySQL on shared hosting plans.
If that happens to be the case for you, there’s a workaround that you can use to emulate the functionality of ROW_NUMBER().
The snippet below shows how you can do this. Note that it consists of two queries, which must both be executed, in the correct order.
It works by first initialising a numeric variable, which you can then increment and add to each record that you retrieve from the database.
SET @row_number = 0;
SELECT
@row_number := @row_number + 1 AS number,
name,
gold,
silver,
bronze
FROM
team
ORDER BY
gold DESC,
silver DESC,
bronze DESC;
+--------+----------------------+------+--------+--------+
| number | name | gold | silver | bronze |
+--------+----------------------+------+--------+--------+
| 1 | Sixcess guaranteed | 5 | 4 | 1 |
| 2 | AMERICA F*** YEAH | 5 | 4 | 0 |
| 3 | Taiwan #1 | 4 | 2 | 1 |
| 4 | Team 4 plays | 3 | 2 | 2 |
| 5 | Five Gals | 3 | 2 | 2 |
| 6 | We ate nine | 0 | 6 | 3 |
| 7 | There was an attempt | 0 | 0 | 0 |
+--------+----------------------+------+--------+--------+
A workaround for RANK()
RANK() is not as easy to emulate as ROW_NUMBER(), but it’s still quite doable. The example below shows how ranks can be generated by joining the team table with itself.
First, the original team table is given an alias, team_result. This where most of the data in our query output will come from.
Then we join the original team table (now called team_result) with another instance of team, which we call better_team. The “better” part is defined in the JOIN condition as any other team (team_result.id != better_team.id) that has won more gold, silver, and/or bronze medals (the entire part after the AND).
We can use GROUP BY and COUNT(better_team.id) to count how many better-performing competitors each team has. This gets us very close to what we want. However, because the best team obviously isn’t bested by any other team, this would make the numbering begin at 0. We can fix this by incrementing the value of COUNT(better_team.id) by 1.
Finally, we sort the results using the newly computed rank field to obtain the same results that we saw earlier when we used RANK().
Easy! (Sort of.)
SELECT
COUNT(better_team.id) + 1 AS rank,
team_result.name,
team_result.gold,
team_result.silver,
team_result.bronze
FROM
team team_result
LEFT JOIN
team better_team ON
team_result.id != better_team.id
AND
(
team_result.gold < better_team.gold
OR
team_result.gold = better_team.gold
AND
team_result.silver < better_team.silver
OR
team_result.gold = better_team.gold
AND
team_result.silver = better_team.silver
AND
team_result.bronze < better_team.bronze
)
GROUP BY
team_result.id
ORDER BY
rank ASC;
+------+----------------------+------+--------+--------+
| rank | name | gold | silver | bronze |
+------+----------------------+------+--------+--------+
| 1 | Sixcess guaranteed | 5 | 4 | 1 |
| 2 | AMERICA F*** YEAH | 5 | 4 | 0 |
| 3 | Taiwan #1 | 4 | 2 | 1 |
| 4 | Team 4 plays | 3 | 2 | 2 |
| 4 | Five Gals | 3 | 2 | 2 |
| 6 | We ate nine | 0 | 6 | 3 |
| 7 | There was an attempt | 0 | 0 | 0 |
+------+----------------------+------+--------+--------+
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