1. MERGE ：可一次性实现对数据的 INSERT, UPDATE, DELETE等，用法如下：
SQL> select * from st_a;
ID NAME
---------- ----------
1 F
100 Z
SQL> select * from st_b;
ID NAME
---------- ----------
1 A
2 B
3 C
100 Z
SQL> merge into st_a a using st_b b on (a.id=b.id)
2 when matched then
3 update set a.name=b.name
4 delete where id=100
5 when not matched then
6 insert values (b.id,b.name);
4 rows merged.
SQL> select * from st_a;
ID NAME
---------- ----------
1 A
2 B
3 C
SQL>
2. WITH：定义的结果集，表名都是临时的，不存储在数据库中，可以将查询的结果集定义别名，用于SQL语句的调用
SQL> with temp_a as (select id,sum(sal) sumsal from st_a group by id), --注意逗号
2 temp_b as (select sum(sumsal)/count(*) avgsal from temp_a)
3 select * from temp_a where sumsal <(select avgsal from temp_b);
ID SUMSAL
---------- ----------
1 7000
其中temp_a和temp_b是WITH语法定义的两个结果集名称，WITH语法后面只能紧跟SELECT语句，且中间不能有任何标点符号