Oliveiros d'Azevedo Cristina wrote: > Howdy, Cedric . > > Before analysing this problem of yours further, I 'd like you to > kindly clarify me some points, please > > > >> >> I have table following tables T0,T1,T2,T3, T1T2 >> with >> -T0(id, fk_T1) >> -T1(id ) >> -T2(id, fk_T3) >> -T1T2(fk_T1,fk_T2) >> -T3 (id) >> >> The table T0 represents sets of T1 items. >> The table T1 represents items. >> The table T3 represents property types. >> The table T2 represents represents property values of a specific type. >> > > > T0.id is not a primary key, is it? all columns with id are Primary keys all columns with fk_T1 are foreign keys > >> For every T1 item of a T0 set I want to know if they do or do not have >> T3 property types and if their values. >> > >> >> next comes view2 as >> >> create view view2 as >> select T2.fk_T3 as my_id >> from T2,T1T2 >> where 1=1 >> and T1T2.fk_T1=23456 >> and T1T2.fk_T2=T2.id; >> >> This will give me all properties types that the T1 item with id 23456 >> has. >> let say this query gives me 4 rows. >> > > > T1T2 is an associative table between items and their property values, > not types, is this correct? YES > If so, I am not realizing why you say that this second view will give > you all property types. Didn't you mean property values? no types because T2.fk_T3 is the foreign key to the property types T3 > > Also, I am not reaching the point of the "1=1" thing. What is the > propose of it, exactly? > Isnt that condition always truth ? Maybe I am lacking some sql > knowledge ... yes it is allways tru is just a typo trick to have all conditions aligned so that you can comment them out easily > > Thanks in advance for advising me > > Best, > Oliveiros > You are to be thanked to getting to my problem
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