Question

I have a database with the following table “responses” with an id and a U.S. state:

*id   *state
1     CA
2     NY
3     NY
4     CO
5     DE

I’m using PHP to output the total number of rows for each of the 50 states in the U.S.

So, my output would look like:
CA: 1
NY: 2
CO: 1
DE: 1
etc…

I know I can run 50 queries like so:

SELECT * 
FROM  `responses` 
WHERE state='CA'

My question is: is there a more efficient way to handle this, or do I need to run 50 queries?

Answer 1

Use a GROUP BY clause:

SELECT state, COUNT(*) FROM `responses` GROUP BY state;

There are many good tutorials on using GROUP BY, and it’s one of the most useful and powerful features of SQL.