postgresql 9.2 - Postgres: How to get json array of multiple boolean columns? -


pg_version: 9.2

i have got table multiple boolean flags.

eg: 

id,flag1,flag2,flag3

problem is, want json array of these flags count like:

[{"title":"flag1","count":2},{"title":"flag2","count":3},{"title":"flag3","count":0}]

how achieve result? tried 

    create or replace function count_test(out json_string text) returns text language plpgsql    $$ begin    select array_to_json(array_agg(rows))into json_string ( select sum(case when flag1 1 else 0 end) flag1, sum(case when flag2 1 else 0 end) flag2, sum(case when flag3 1 else 0 end) flag3 flags ) rows;   end; $$;

but can [{"flag1":2,"flag2":2,"flag3":0}]

awaiting immediate response.

you aggregate row_to_json results array , try casting json , on, considering limited json support in 9.2 i'd build json string, eg:

postgres=# flags(id,flag1,flag2) (values(1,true,true),(2,false,true)) , s (select sum(flag1::int) f1, sum(flag1::int) f2 flags) select concat('[{"title":"flag1","count":',f1,'},{"title":"flag2","count":',f2,'}]')::json s;                           concat -----------------------------------------------------------  [{"title":"flag1","count":1},{"title":"flag2","count":1}] (1 row)

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