如何在SQL查询中创建配对？

Question

Could anyone tell me how to create pairs in MySQL. If you see the below query

select A.cakeid , A.ingredid from Contain as A inner join (select 
    cakeid, count(cakeid)
from
    Contain
group by cakeid
having count(cakeid) >= 3 ) as B on A.cakeid = B.cakeid 

OUTPUT:

Cakeid Ingredid
'1', '1'
'1', '3'
'1', '4'
'3', '1'
'3', '4'
'3', '5'
'5', '1'
'5', '2'
'5', '4'
'6', '1'
'6', '2'
'6', '3'
'6', '5'
'7', '1'
'7', '2'
'7', '3'
'7', '4'
'8', '1'
'8', '2'
'8', '3'

Could anyone tell me how can I create pairs of Cakeid which uses atleast three common ingredient ? For example, 6 and 7 are one pair which have three common ingredient.

Answer 1

Self-join

select c1.cakeid cake1, c2.cakeid cake2, count(*) matching_Ingredid  
from Contain c1
join Contain c2 
    on c1.cakeid < c2.cakeid and c1.Ingredid = c2.Ingredid
group by c1.cakeid, c2.cakeid
having count(*) >= 3

Answer 2

The query below will give you the cakeids next to each other that contain more than 3 common ingredients.

select c1.cakeid as cakeid1, c2.cakeid as cakeid2 from
contain c1 inner join contain c2 on c1.ingredid=c2.ingredid and c1.cakeid<c2.cakeid
group by c1.cakeid, c2.cakeid
having count(*)>=3

To get the list you wanted from this, you need to join the above query once on the cakeid1, and once on the cakeid2 to the contain table again:

select c3.cakeid, c3.ingredid from content c3 inner join
(select c1.cakeid as cakeid1, c2.cakeid as cakeid2 from
contain c1 inner join contain c2 on c1.ingredid=c2.ingredid and c1.cakeid<c2.cakeid
group by c1.cakeid, c2.cakeid
having count(*)>=3) t1 on c3.cakeid=t1.cakeid1
union all
select c4.cakeid, c4.ingredid from content c4 inner join
(select c1.cakeid as cakeid1, c2.cakeid as cakeid2 from
contain c1 inner join contain c2 on c1.ingredid=c2.ingredid and c1.cakeid<c2.cakeid
group by c1.cakeid, c2.cakeid
having count(*)>=3) t2 on c4.cakeid=t2.cakeid2