Re: protected ON DELETE CASCADE

i neglected to show it properly

have tables A, B, C, D PLUS a few others

A <- B

     F
     |
     v
A <- C <- D
     ^
     |
     E

i want to delete from C and cascade any delete to E or F but not if
there are records in D

what i have done is to have ON DELETE CASCADE on C's primary

but force deletes to C through a function that will delete from C only
if there is no records in D

but i would like to believe there is a better way - a way that does not
require that i do all my deletes through a function

cheers

murray



Oliver Elphick wrote:
>
> Murray Hobbs wrote:
>   >
>   >here's my problem
>   >
>   >i have tables A, B, C, D
>   >
>   >A <- B
>   >A <- C <- D
>   >
>   >i want to maintain integrity so that if A is deleted from then so is
>   >anything referencing from B and C - no problem ON DELETE CASCADE
>   >
>   >but if there are any D's that point back to A (through composite key in
>   >C) i don't want the delete to go ahead - at all - i want an error
>   >message and condition
>
> If the reference from D to C uses ON DELETE RESTRICT (or NO ACTION), that
> should fail and thus cause the original DELETE to fail.
>
> --
> Oliver Elphick                                Oliver.Elphick@lfix.co.uk
> Isle of Wight                              http://www.lfix.co.uk/oliver
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