mysql select in another select group: how many people in downline?

Question

Hello i've a table similar to this one:

id     sponsor     name
------------------------
1      0          Sasha
2      1          John
3      1          Walter
4      3          Ashley
5      1          Mark
6      4          Alexa       
7      3          Robert
8      3          Frank
9      4          Marika
10     5          Philip
11     9          Elizabeth

when i choose an ID (call it MYCHOICE) i want know all the name of people who has sponsor like MYCHOICE... is simply:

select * from tablename where sponsor=MYCHOICE

but... here is the problem... i would know how many people there is in the downline of this results... so... how many records there are with sponsor like each id.

if i choose id 1 result should be

id  name     downline
----------------------
2   John     0              (noone with sponsor=2)
3   Walter   3              (3 with sponsor=3: ashley, robert, frank)
5   Mark     1              (1 with sponsor=5: philip)

if i choose id 4 result should be

id  name     downline
----------------------
6   Alexa    0
9   Marika   1   (1 with sponsor=9: Elizabeth)

i try this "bad solution" if mychoice is 1

select sponsor,count(*) as downline from tablename where sponsor in (select id from tablename where sponsor=1) group by sponsor order by downline desc

result of this query is

sponsor  downline
---------------------
3        3
5        1

there are 2 problems: - names are not rights and is not that i want - the count 0 "2|John|0" in the example dont appears

thank u for advice and help, sorry for english, N.

Answer 1

SELECT  child.id,
        child.name,
        COUNT(grandchild.sponsor) downline
FROM    TableName child
        INNER JOIN TableName parent
            ON  child.sponsor = parent.id AND
                parent.id = ?              -- << user choice
        LEFT JOIN TableName grandchild
            ON child.id = grandchild.sponsor
GROUP   BY child.id, child.name

• SQLFiddle 演示

正如您所看到的，该表自身连接了两次。使用的第一个连接获取与您的user_choiceINNER JOIN关联的记录。使用的第二个连接获取与user_choice中的记录关联的所有记录。SponsorLEFT JOIN