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Editorial Team
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Asked: 2026-05-26T01:20:08+00:00

user_drug.user_id is constrained by Foreign Key drug.id (which is a Primary Key). Table structure

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user_drug.user_id is constrained by Foreign Key drug.id (which is a Primary Key).

Table structure is as follows:

user
id    name  income
1     Foo   10000
2     Bar   20000
3     Baz   30000

drug
id    name
0     Marijuana
1     Cocaine
2     Heroin

user_drug
user_id drug_id
1       1
1       2
2       1       
2       3
3       3

Are there any drawbacks to starting drug.id at 0? I have a feeling that that will make things more natural with PHP since arrays also start at 0, but I want to make sure there aren’t any drawbacks with using ‘0’ for an id (e.g. it might be interpreted as null or some other strange potential occurrence/conflict).

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1 Answer

  1. Editorial Team

    If its an AUTO INCREMENT col, zero is a special value which shouldnt be used, but this can be overcome. If its a foreign key and non AUTO INCREMENT, any value is OK. Zero will not be interpreted as anything other than a zero if your column definition is correct (null values appear as NULL, which is distinct from zero)

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