sql - shared relationships in database -


sorry ignorant.... trying set database of 5 tables.... truck_fleets, cabs, trailers, tyres, tyre_pressures. should straight forward except "tyres" needs child of both "cab" , "trailer". both cab of truck , trailer of truck have tyres!

in setting end 2 keys in "tyres" 1 of satisfied. tyre belongs either cab or the trailer.

any suggestions or reference can read please.

thanks

try 2 relation tables. 1 connects cabs tyres, call cab_tyres , 1 connects trailers tyres, call trailer_tyres.

each table holds 2 id's. 

cab_tyres:   int cab_id   //fk cab table  int tyre_id  //fk tyre table  trailer_tyres:   int trailer_id //fk trailer table  int tyre_id    //fk tyre table

to elaborate little, theory here entity relations entities, , typed according things relate. don't mix types normally, have 2 relation tables.

if wish relate cab , it's trailer, relation entity , on.


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