以此备忘：
xxxxxx@ubuntu:~/sqlite/SQLite-036ebf72_orig_3.18.2$ ./sqlite3 t.db SQLite version 3.18.2 2017-06-17 09:59:36 Enter ".help" for usage hints. sqlite> create table t1(id integer primary key autoincrement, data text); sqlite> create table t2(id integer primary key autoincrement, data text); sqlite> insert into t1(data) values('t1_d1'); sqlite> insert into t1(data) values('t1_d2'); sqlite> insert into t2(data) values('t2_d1'); sqlite> insert into t2(data) values('t2_d2'); sqlite> select * from t1 union select * from t2; 1|t1_d1 1|t2_d1 2|t1_d2 2|t2_d2 sqlite> select * from(select * from(select * from t1 limit 1) union select * from(select * from t2 limit 1)); 1|t1_d1 1|t2_d1 sqlite> select * from(select * from(select * from t1 limit 1) union all select * from(select * from t2 limit 1)); 1|t1_d1 sqlite> sqlite> sqlite> select * from(select * from(select * from t1 limit 2) union all select * from(select * from t2 limit 2)); 1|t1_d1 2|t1_d2 sqlite> select * from(select * from(select * from t1) union all select * from(select * from t2 limit 2)); 1|t1_d1 2|t1_d2 1|t2_d1 2|t2_d2 sqlite> select * from(select * from(select * from t1 limit 2) union all select * from(select * from t2)); 1|t1_d1 2|t1_d2 sqlite> select * from(select * from(select * from t1 limit 2) union select * from(select * from t2 limit 2)); 1|t1_d1 1|t2_d1 2|t1_d2 2|t2_d2 sqlite> select * from(select * from(select * from t1) union select * from(select * from t2 limit 2)); 1|t1_d1 1|t2_d1 2|t1_d2 2|t2_d2 sqlite> select * from(select * from(select * from t1 limit 2) union select * from(select * from t2)); 1|t1_d1 1|t2_d1 2|t1_d2 2|t2_d2 sqlite>
备注：aHR0cCUzQS8vd3d3LmNuYmxvZ3MuY29tL3poaGQv