mysql - FInd relationships within three products -

i using php , mysql

if have following tables

items ---- |order_id|sku| |------------| |   1    | | |   1    | b | |   1    | c | |   1    | d | |   1    | e |  |   2    | b | |   2    | c | |   2    | d | |   3    | d | |   3    | e | |   3    | f |  |   4    | |  |   4    | b |  |   4    | c | |   4    | f | -------------- 

i retrieve following info:

| original_sku | bought_with_a | bought_with_a | times_bought_together | |--------------|---------------|---------------|-----------------------| |            |      b        |        c      |           2           | |       b      |             |        c      |           2           |   |       b      |      c        |        d      |           2           | |       c      |      b        |        d      |           2           |    etc etc 

i trying count number of times 3 products bought together. extension question: finding products customers bought together

you should follow same approach in solution 3-way combinations:

select i1.sku sku1, i2.sku sku2, i3.sku sku3, count(*) bought_together items i1 join      items i2      on i1.order_id = i2.order_id , i1.sku <> i2.sku join      items i3      on i1.order_id = i3.order_id , i3.sku not in (i1.sku, i2.sku) group i1.sku, i2.sku, i3.sku; 

you should able readily figure out how extend more products, adding more joins.