Remember that casting can do weird things, so whatever you try, make sure it's doing what you want.
sqlite> create table t1 (a text unique);
sqlite> create table t2 (b integer);
sqlite> insert into t1 values ('1'), ('1.0'), ('1xyz');
sqlite> insert into t2 values (1);
sqlite> select * from t2 left outer join t1 on a = b;
QUERY PLAN
|--SCAN TABLE t2
`--SCAN TABLE t1
b|a
1|1
1|1.0
sqlite> select * from t2 left outer join t1 on a = cast(b as text);
QUERY PLAN
|--SCAN TABLE t2
`--SEARCH TABLE t1 USING COVERING INDEX sqlite_autoindex_t1_1 (a=?)
b|a
1|1
sqlite> select * from t2 left outer join t1 on cast(a as int) = b;
QUERY PLAN
|--SCAN TABLE t2
`--SCAN TABLE t1
b|a
1|1
1|1.0
1|1xyz