Question

idI have a table like this

|----|-----------|--------|
| ID | Ethnicity | Gender |
| 1  |    2      |   1    |
| 2  |    3      |   1    |
| 3  |    4      |   2    |
|----|-----------|--------|
etc ....

And I’m trying to get back a set of results that show me ethnicities group by male(1) and female(2)

So the result row would in this example would be:

Ethnicity    Male    Female
    2         1        0
    3         1        0
    4         0        1

So far I’m close with to what I want with:

SELECT ethnicity, 
(SELECT 
        count(id)
    FROM
        table_name
    WHERE
        gender = '2' ) as female,
(SELECT 
        count(id)
    FROM
        table_name
    WHERE
        gender = '1') as male
FROM table_name
GROUP BY ethnicity

Which gives me:

Ethnicity    Male    Female
2            2        1
3            2        1
4            2        1

But need the count(id) to only be a count of the adno of that ethnicity row if that makes sense.

Answer 1

Try this instead:

SELECT 
  ethnicity, 
  SUM(CASE WHEN gender = 1 THEN 1 ELSE 0 END) AS female,
  SUM(CASE WHEN gender = 2 THEN 1 ELSE 0 END) AS Male
FROM students
GROUP BY ethnicity;

The above should work in virtually any SQL product, not just in MySQL. If you like, however, you can also use this version, which employs MySQL’s implicit conversion of booleans to ints (true -> 1, false -> 0):

SELECT 
  ethnicity, 
  SUM(gender = 1) AS female,
  SUM(gender = 2) AS Male
FROM students
GROUP BY ethnicity;