字段中每个值的MYSQL计数

Question

I have a database with the following table "responses" with an id and a US 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 US

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.

Answer 2

You can use MySQL's GROUP BY clause which will group all of the results by the state :

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