database - SQL design for similar tables with few column differences -


i working on application deals questions , answers. answers can of different types ranging int, text, image, option, etc.. , wonder if practice separate different tables below?

question            questionanswer --------            ------------- int id               int questionid int typeid           int answerid  textanswer          imageanswer    optionanswer        intanswer ----------          -----------    ------------        --------- int answerid        int answerid   int answerid        int answerid nvarchar value      binary value   int value           int value                                    int optiontypeid

i thought aggregating 1 single answer table filled nullable fields , afraid might introduce bugs if not careful. idea or design practice in separating different types of answers? or perhaps there better approach ? thanks!

the question of 1 table (for answers), 4 tables (for each type of answer), or 5 tables (one answers, 1 specific each type) depends on 2 factors.

the important is: how data used? second is: database using?

let me dispense second part first. databases (notably postgres) have built-in support table inheritance. can read [documentation]; 1; want.

for other databases how choose? well, have table answerid in it. suggests want single entity, automatically generated primary key.

so, store information in table or not? 1 argument of putting columns in single table simplicity: data in 1 place. can enforce null-ness of values using check constraints. 1 downside adding new type requires modifying table.

another alternative have each of specific tables. can use answerid primary key, having foreign key answers. makes each add new types. however, can cumbersome ensure answer has 1 type. joins bit more complicated.

under circumstances, tend go 1 table , proliferation of columns, if knew expected range of types in advance.


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