Query and get three expected results - mysql

Question

SELECT
(
`members`.`id`
SELECT COUNT(`members`.`id`) FROM `members` WHERE `gender` = 0 AS `Unknown`
SELECT COUNT(`members`.`id`) FROM `members` WHERE `gender` = 1 AS `Female`
SELECT COUNT(`members`.`id`) FROM `members` WHERE `gender` = 2 AS `Male`
) FROM `members` INNER JOIN `mapMember`
ON `mapMember`.`id` = `members`.`id`
WHERE `mapMember`.`mapper_id` = 3
My expected result:
Unknown Female Male
0 1 3
However I get SYNTAX error. Cant' figure out what's wrong.
I also tried:
SELECT COUNT(`members`.id) AS `members`, `gender`
FROM `members` INNER JOIN `mapMember`
ON `mapMember`.`id` = `members`.`id`
WHERE `mapMember`.`mapper_id` = 3 GROUP BY `gender` ORDER BY `gender` ASC
Which gives me almost the result I want to have, the only difference is If the there are no members with the given gender, there won't be a 0 result back. (no row that is) I always expect three rows back.

Answer 1

SELECT
sum(if (`gender` = 0, 1,0)) as `Unknown`,
sum(if (`gender` = 1, 1,0)) as `Female`,
sum(if (`gender` = 2, 1,0)) as `Male`
FROM `members` INNER JOIN `mapMember`
ON `mapMember`.`id` = `members`.`id`
WHERE `mapMember`.`mapper_id` = 3

Answer 2

SELECT * FROM
(
SELECT `members`.`id`,COUNT(`members`.`id`) AS `Unknown` FROM `members` WHERE `gender` = 0
UNION
SELECT `members`.`id`,COUNT(`members`.`id`) AS `Female` FROM `members` WHERE `gender` = 1
UNION
SELECT `members`.`id`,COUNT(`members`.`id`) AS `Male` FROM `members` WHERE `gender` = 2
) Z INNER JOIN `mapMember`
ON `mapMember`.`id` = `Z`.`id`
WHERE `mapMember`.`mapper_id` = 3

Answer 3

Others have given you solutions, so I mainly tell you where you went wrong with your own statement.
COUNT(column_name) simply counts records where column_name is not null. members.id is not null, so you simply count all records from members. You need a where clause instead limiting the counted records to the member id in question.
Sub queries must be in parentheses.
Here is your statement re-written. It is not good though, because you query the same table again and again. I just wanted to use your statement and only correct errors:
SELECT
`members`.`id`,
(SELECT COUNT(*) FROM `members` u WHERE `gender` = 0 AND u.id = members.id) AS `Unknown`
(SELECT COUNT(*) FROM `members` f WHERE `gender` = 1 AND f.id = members.id) AS `Female`
(SELECT COUNT(*) FROM `members` m WHERE `gender` = 2 AND m.id = members.id) AS `Male`
FROM `members` INNER JOIN `mapMember`
ON `mapMember`.`id` = `members`.`id`
WHERE `mapMember`.`mapper_id` = 3;
Now it's syntactically correct. However, as a member record has exactly one gender, you will always get records with 0-0-1 or 0-1-0 or 1-0-0. So you don't really want to select members and have the counts per member.
Here is a better statement querying the tables just once, counting over all records rather than per member and providing better readabilty by using an IN clause for mapmember. (You can as well replace the IN clause with an EXISTS clause, which is sometimes faster.)
select
sum( case when gender = 0 then 1 else 0 end ) as unknown,
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 members
where id in (select id from mapmember where mapper_id = 3);
(BTW: Is the mapmember id really a members id? It looks strange to have a table with a column named id and this not being the id of the table itself but the id of another table actually.)
EDIT: I just notice you use MySQL. There you have a boolean data type you can use:
select
sum( gender = 0 ) as unknown, sum( gender = 1 ) as female, sum( gender = 2 ) as male
from members
where id in (select id from mapmember where mapper_id = 3);
This is no longer standard SQL, because it uses an enhancement from MySQL.