如何筛选出具有cat又具有bid的唯一的username，在下面的数据表中？

如果是PostgreSQL可以使用窗口查询来解决这个问题：

digoal=# drop table tbl;;
DROP TABLE
digoal=# 
digoal=# create table tbl(username text, store text, item text, value int);
CREATE TABLE
digoal=# insert into tbl values ('kaixin','lease','bid',1);
INSERT 0 1
digoal=# insert into tbl values ('kaixin','lease','bid',2);
INSERT 0 1
digoal=# insert into tbl values ('kaixin','lease','bid',3);
INSERT 0 1
digoal=# insert into tbl values ('kaixin','lease','cat',3);
INSERT 0 1
digoal=# insert into tbl values ('kaixin','lease','cat',4);
INSERT 0 1
digoal=# insert into tbl values ('kaixin','lease','cat',5);
INSERT 0 1
digoal=# insert into tbl values ('kaixin123','lease','cat',6);
INSERT 0 1

digoal=# select * from tbl;
 username  | store | item | value 
-----------+-------+------+-------
 kaixin    | lease | bid  |     1
 kaixin    | lease | bid  |     2
 kaixin    | lease | bid  |     3
 kaixin    | lease | cat  |     3
 kaixin    | lease | cat  |     4
 kaixin    | lease | cat  |     5
 kaixin123 | lease | cat  |     6
(7 rows)

digoal=# select distinct username from (select array_agg(item) over(partition by username) arr,username from tbl) t where arr @> array['bid','cat'];
 username 
----------
 kaixin
(1 row)