CODEWITHSUNDEEP
erlangmnesia
Amin
Amin

Reputation: 755

Select a value in complex mnesia table

Im new in Erlang and Mnesia. I created a table in mnesia:

-record(user, {name="", game=""}).
-record(base, {user=#user{}, score=0}).


init() ->
    mnesia:create_schema([node()]),
    mnesia:start(),
    mnesia:create_table(base, [{attributes, record_info(fields, base)}]),
    mnesia:stop().

Now i want to select all rows of table base where the "game" is a certain value. i wrote this function but it does not work when Game variable is not equal to "".

exec(base, Game) when is_list(Game)->
F = fun() ->
        if
            Game =/= "" ->
                Q = qlc:q([{R#base.user#user.name, R#base.score} || R <- mnesia:table(base), R#base.user#user.game == Game]);
            true ->
                Q = qlc:q([{R#base.user, R#base.score} || R <- mnesia:table(base)])
        end,
        qlc:e(Q)
    end,
{_, Data} = mnesia:transaction(F),
Data;

How can i make my query to it as i want?

Upvotes: 0

Views: 218

Answers (1)

Amin
Amin

Reputation: 755

Solved. I changed my function:

exec(base, Game) when is_list(Game)->
    F = fun() ->
            if
                Game =/= "" ->
                    Q = qlc:q([{Name, Score} || #base{user={Name, G}, score=Score} <- mnesia:table(base), G == Game]);
                true ->
                    Q = qlc:q([{R#base.user, R#base.score} || R <- mnesia:table(base)])
            end,
            qlc:e(Q)
        end,
    {_, Data} = mnesia:transaction(F),
    Data;

Upvotes: 1

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