select statement extremly slow - ios

Question

I'm creating 4 tables and select from them afterwards. Selecting works perfectly for the first 3 select statements, but the 4th one takes about 10 seconds on the iPhone simulator, and 5 seconds on the sqlite3 console.
Also I get 0 results on the iPhone simulator, but 1 on the console. But that's a problem I want to solve after I solved the performance issue.
I read something about indexes and how they can improve the performance, but I have no clue how to implement them in my code.
sql0 = [[NSString alloc]initWithFormat:#"
create table v%i
as select id_produkt
from v%i natural join produkt_eigenschaft
where id_eigenschaft =
(select id_eigenschaft from eigenschaft where at = '%#')",counter,counter-1,selectedStringItem];
and afterwards:
NSString *sqleig = [[NSString alloc]initWithFormat:#"
select at
from eigenschaft
where id_eigenschaft IN
(select distinct id_eigenschaft
from produkt_eigenschaft
where id_produkt IN (select * from v%i))
AND rubrik = '%i'",counter-1, [sender tag] + 1];
Why is this statement executed so slowly? And how can I solve it?
Thanks in advance.
EDIT: explain query plan and .schema
explain query plan create table v3 as select id_produkt from v2 natural join produkt_eigenschaft where id_eigenschaft = (select id_eigenschaft from eigenschaft where at = '101-170');
0|0|1|SCAN TABLE produkt_eigenschaft (~100000 rows)
0|0|0|EXECUTE SCALAR SUBQUERY 1
1|0|0|SEARCH TABLE eigenschaft USING AUTOMATIC COVERING INDEX (at=?) (~7 rows)
0|1|0|SEARCH TABLE v2 USING AUTOMATIC COVERING INDEX (id_produkt=?) (~7 rows)
explain query plan select at from eigenschaft where id_eigenschaft IN (select distinct id_eigenschaft from produkt_eigenschaft where id_produkt IN (select * from v3)) AND rubrik = '5';
0|0|0|SCAN TABLE eigenschaft (~10000 rows)
0|0|0|EXECUTE LIST SUBQUERY 1
1|0|0|SCAN TABLE produkt_eigenschaft (~100000 rows)
1|0|0|EXECUTE LIST SUBQUERY 2
2|0|0|SCAN TABLE v3 (~1000000 rows)
1|0|0|USE TEMP B-TREE FOR DISTINCT
CREATE TABLE eigenschaft (id_eigenschaft integer,rubrik integer,en text,at text,ba text,bg text,hr text,cz text,hu text,pl text,ro text,ru text,rs text,sk text,si text);
CREATE TABLE farbe (id_farbe integer,hexcode text,farbton integer,farbname text);
CREATE TABLE produkt (id_produkt integer,code text,pdf_link text,image_link text,image_small blob,link text,en text,at text,ba text,bg text,hr text,cz text,hu text,pl text,ro text,ru text,rs text,sk text,si text,active integer);
CREATE TABLE produkt_eigenschaft (id_produkt integer,id_eigenschaft integer);
CREATE TABLE produkt_farbe (id_produkt integer,id_farbe integer);
CREATE TABLE produkt_surface (id_surface integer,id_produkt integer,image_link text);
CREATE TABLE produkt_text (id_produkt integer,en text,at text,ba text,bg text,hr text,cz text,hu text,pl text,ro text,ru text,rs text,sk text,si text);
CREATE TABLE rubrik (id integer,en text,at text,ba text,bg text,hr text,cz text,hu text,pl text,ro text,ru text,rs text,sk text,si text);
CREATE TABLE v0(id_produkt INT);
CREATE TABLE v1(id_produkt INT);
CREATE TABLE v2(id_produkt INT);
CREATE TABLE v3(id_produkt INT);

Answer 1

Solved it with indexes.
create index i on produkt_eigenschaft (id_eigenschaft)
Call this once before selecting