1.update 语句
update table set [column,column......] where column =''
示例： update customers
set cust_credit_limit = 20000
where cust_id = 2789;
2.delete 语句
delete from table where 条件
示例; delete from customers
where cust_state_province = 'QT';
备注；truncate customers 也可以删除该表的所有记录，但是它在出错不允许回滚的
3.数据排序
order by
示例: select cust_id,cust_state_province, cust_credit_limit
from customers
where cust_credit_limit = 15000
and cust_state_province in ('QT','CT')
order by cust_state_province ,cust_id ;
备注：oracle 默认的是按照升序排序，如果需要降序就 要在排序字段后面添加desc
示例：select cust_id ,cust_state_province,cust_credit_limit
from customers
where cust_credit_limit =15000
and cust_state_province in ('UT','CT')
order by cust_state_province ,cust_id desc
4.group by
group by 主要是分组 来进行求和 或者其它运算
示例：select prod_subcategory,avg(amout_sold)
from sales s ,products p
where s.prod_id = p.prod_id
and prod_category = 'Electronics'
group by prod_subcategory ;
5.having
在对group by 操作的使用having 字句可以限制返回的组
示例：select prod_subcategory,avg(amout_sold)
from sales s ,products p
where s.prod_id = p.prod_id
and prod_category = 'Electronics'
group by prod_subcategory
having avg(amout_sold) > 300;
6.子查询
sql 一个强大功能就是创建子查询，即查询中嵌套查询。这一功能使得基于另一结果或者其他结果集进行查询成为可能
示例：
select prod_id ,prod_name ,prod_category
from products
where prod_list_price =
(
select max(prod_list_price) from products
);
7:集合操作
union 返回两表中无任何重复的所有行
示例：select * from x
union
select *from y
union all 返回两表中所以行（包含重复）
示例:select * from x
union all
select *from y
intersect 返回两表中都存在的行
示例:select * from x
intersect
select *from y