Compare date in two year - mysql

Question

I have a table of population that I want to compare population in two year.
My table structure:
id (auto increment), type (man,woman,child), population (1 to 10000), date
I want run two under query and show into one table result:
query1:
SELECT type,count(population) as count_of_year1
FROM population
where date between '2013-01-01' and '2013-01-24'
GROUP BY type
query2:
SELECT type, count(population) as count_of_year2
FROM population
where date between '2014-01-01' and '2014-01-24'
GROUP BY type
I need this result :
| Type | population in year2013| population in year 2014
How to do this?

Answer 1

Use case expressions to do conditional counting:
SELECT type,
count(case when date between '2013-01-01' and '2013-01-24' then population end) as count_of_year1,
count(case when date between '2014-01-01' and '2014-01-24' then population end) as count_of_year2
FROM population
GROUP BY type
Add this where clause to speed things up if needed:
where date between '2013-01-01' and '2013-01-24'
or date between '2014-01-01' and '2014-01-24'

Answer 2

As population can have a value from 1 to 10000, I assume you want SUM() here not COUNT().
I'd have a separate table for types:
population_type - id, title
population - id, type_id (references type.id), population, date
Then I prefer using JOINs here:
SELECT pt.title type,
COALESCE(y1.total_population,0) population_2013,
COALESCE(y2.total_population,0) population_2014
FROM population_type pt
LEFT JOIN (
SELECT type_id,
SUM(population) total_population,
FROM population
WHERE date >= '2013-01-01'
AND date < '2013-01-24' + INTERVAL 1 DAY
GROUP BY type
) y1
ON y1.type_id = pt.id
LEFT JOIN (
SELECT type_id,
SUM(population) total_population,
FROM population
WHERE date >= '2014-01-01'
AND date < '2014-01-24' + INTERVAL 1 DAY
GROUP BY type
) y2
ON y2.type_id = pt.id
This way you are only summing through what you need each time and the query is more modular.