sql - Query attributes, where one attribute is missing -

i have question regarding query. there 2 tables:

objects table: ============== object id   date 1       2016-03-15 2       2016-01-20  attributes table: ================= parent id   attribute   attributedata 1       size        xl 2       size        s 2       price       20  query join data this: ========================================== objet id    size    price 1       xl  null 2       s   20  this: ========================================== objet id    size    price 2       s   20 

a left join doesn't - because there no entry in attribute table price id1.

i sorry beein such newbie on this.

glad help.

steffen

i think conditional aggregation want:

select parentid,        max(case when attribute = 'size' attributedata end) size,        max(case when attribute = 'price' attributedata end) price attributes group parentid; 

using left join do:

select o.*, s.attributedata size, p.attributedata price objects o left join      attributes s      on o.objectid = s.parentid , s.attribute = 'size' left join      attributes p      on o.objectid = p.parentid , p.attribute = 'price'; 

note work, condition on attribute name needs in on clause, not where clause.