sql - Can I choose what table to JOIN based on a CASE? -

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for instance, if have table owner this:

 +-------------------------------+ |  id  catid   dogid   fishid   | +-------------------------------+ |  1   464    (null)  (null)    | |  2  (null)  (null)    93      | +-------------------------------+

and query similar this:

select * owner join cat on owner.catid = cat.id join dog on owner.dogid = dog.id join fish on owner.fishid = fish.id;

but instead of joining every time, can use case statement (or similar) "only join cat if value in catid column not null". possible?

each owner id have 1 of cat, dog, or fish (i.e. each owner, 1 not null).

no, can use left join values:

select owner.*, coalesce(cat.col, dog.col, fish.col) col owner left join      cat      on owner.catid = cat.id left join      dog      on owner.dogid = dog.id left join      fish      on owner.fishid = fish.id;

you can choose (first) 1 matches in select.


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